Portable gas sensing instrument

ABSTRACT

A portable electrochemical or combustible lower explosive limit gas sensing apparatus includes a housing comprising at least one exterior surface and an interior space. At least one depression is formed in the at least one exterior surface and is adapted to accommodate, at least in part, components of an electrochemical gas sensor or a combustible LEL gas sensor. A processing unit is disposed in the interior space of the housing and is in electrical communication with the electrochemical gas sensor or the combustible LEL gas sensor.

CLAIM TO PRIORITY

This application is a continuation of the following U.S. patentapplication, which is incorporated by reference in its entirety: U.S.Ser. No. 15/665,034, filed Jul. 31, 2017.

U.S. Ser. No. 15/665,034 claims the benefit of the following provisionalapplications, each of which is hereby incorporated by reference in itsentirety: U.S. Ser. No. 62/384,798, filed Sep. 8, 2016; U.S. Ser. No.62/409,706, filed Oct. 18, 2016; U.S. Ser. No. 62/397,587, filed Sep.21, 2016; U.S. Ser. No. 62/384,803, filed Sep. 8, 2016; and U.S. Ser.No. 62/463,230, filed Feb. 24, 2017.

U.S. Ser. No. 15/665,034 is a continuation-in-part of U.S. Ser. No.15/491,311, filed Apr. 19, 2017, which is hereby incorporated byreference in its entirety. U.S. Ser. No. 15/491,311 claims the benefitof the following provisional applications, each of which is herebyincorporated by reference in its entirety: U.S. Ser. No. 62/324,573,filed Apr. 19, 2016; U.S. Ser. No. 62/364,935, filed Jul. 21, 2016; andU.S. Ser. No. 62/385,688, filed Sep. 9, 2016.

U.S. Ser. No. 15/665,034 is also related to the following U.S. patentsand patent applications each of which is incorporated by referenceherein in its entirety: U.S. Pat. No. 9,000,910 filed on Jun. 24, 2011,U.S. Pat. No. 9,575,043 filed Apr. 1, 2015, U.S. patent application Ser.No. 15/376,823, filed Dec. 13, 2016, U.S. Pat. No. 6,338,266 filed Apr.5, 2000, U.S. Pat. No. 6,435,003 filed Nov. 8, 2001, U.S. Pat. No.6,888,467 filed Dec. 10, 2002, U.S. Pat. No. 6,742,382 filed Dec. 24,2002, U.S. Pat. No. 6,442,639 filed Apr. 19, 2000, U.S. Pat. No.7,007,542 filed Jun. 16, 2003, and U.S. Patent Application Serial No.2016/0209386, entitled MODULAR GAS MONITORING SYSTEM and filed on Jan.15, 2016.

BACKGROUND Field

This disclosure relates to portable gas sensing instruments that mayinclude various types of sensors, such as electrochemical sensors andLEL (lower explosive limit) sensors.

SUMMARY

In an aspect, a tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to multi-gas detection instrument operators; receivingtemporary assignment information at the safety device when an NFC radioof the safety device is brought in proximity to at least one of theplurality of NFC tags; and tagging safety device data with the temporaryassignment information. In this aspect and others disclosed herein, theprogramming of the plurality of NFC tags is not required. In fact,pre-programmed NFC tags may be purchase for use in the systems andmethods disclosed herein. The operations further include storing thetagged safety device data in a safety device data log. The operationsfurther include wirelessly transmitting the tagged safety device data toat least one of a cloud-based or other remote log and a second device.The operations further include removing the temporary assignment bybringing the safety device into proximity to the at least one NFC tagagain. The safety device is a multi-gas detection instrument, a gasdetection instrument, or at least one of a respirator, a harness, alighting device, a fall arrest device, a thermal detector, a flamedetector, and a chemical, biological, radiological, nuclear, andexplosives (CBRNE) detector.

In an aspect, a tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to safety device operators; receiving assignment informationat the safety device when an NFC radio of the safety device is broughtin proximity to at least one of the plurality of NFC tags; andtriggering one or more of an alarm and a message upon detection of asafety event, wherein the trigger is filtered by the temporaryassignment information. The assignment tags for identifying individualsare programmed with information including one or more of a name, a size,a weight, a typical work location, a job function, a typical instrumentused, a pre-existing concern, a language known, a prior alarm, a priorgas event, a prior safety event, and a prior message. The assignmenttags for identifying locations are programmed with information includingone or more of a location within a space, a GPS location, an equipmentat the location, a fuel source at the location, a known hazard at thelocation, a typical gas concentration for the location, an environmentalcondition for the location, a recent gas event, a recent man down alarm,a recent alarm, and a recent message. Triggering further comprisesapplying a filter based on the assignment tag's programmed information.The safety device is at least one of a multi-gas detection instrument, agas detection instrument, a respirator, a harness, a lighting device, afall arrest device, a thermal detector, a flame detector, and achemical, biological, radiological, nuclear, and explosives (CBRNE)detector. The safety event is a gas event.

In an aspect, an industrial safety monitoring system includes a personalNFC tag assigned to a worker, wherein the tag assigned to the workercomprises information of the identity of the worker; a plurality oflocation NFC tags assigned to locations, each location tag placed in alocation comprising information of the location in which the locationtag is placed; at least one portable environmental sensing devicedetecting data of an environmental parameter, the at least one portableenvironmental sensing device configured to (i) read the personal NFC tagand to transmit the information of the identity of the worker using thesensing device, and (ii) read at least one of the plurality of locationNFC tags and to transmit the information of the location of a locationtag read by the at least one portable environmental sensing device; andat least one processor in communication with the at least one portableenvironmental sensing device and receiving from the at least oneportable environmental sensing device (i) detected data of anenvironmental parameter, (ii) the information of the identity of theworker using the at least one portable environmental sensing device, and(iii) information of the location of a location tag read by the at leastone portable environmental sensing device, wherein the at least oneprocessor is programmed to determine an environmental parameter of theworker using the sensing device and the location of the determinedenvironmental parameter. The system further includes a memory incommunication with the at least one portable environmental sensingdevice that stores the detected data and the information in a portableenvironmental sensing device data log. The system further includes awireless transmitter that transmits the detected data and theinformation to at least one of a cloud-based or other remote log and asecond portable environmental sensing device. The assignment tags foridentifying workers are programmed with information including one ormore of a name, a size, a weight, a typical work location, a jobfunction, a typical instrument used, a pre-existing concern, a languageknown, a prior alarm, a prior gas event, a prior safety event, and aprior message. The assignment tags for identifying locations areprogrammed with information including one or more of a location within aspace, a GPS location, an equipment at the location, a fuel source atthe location, a known hazard at the location, a typical gasconcentration for the location, an environmental condition for thelocation, a recent gas event, a recent man down alarm, a recent alarm,and a recent message. The at least one portable environmental sensingdevice is at least one of a multi-gas detection instrument, a gasdetection instrument, a respirator, a harness, a lighting device, a fallarrest device, a thermal detector, a flame detector, and a chemical,biological, radiological, nuclear, and explosives (CBRNE) detector.

In an aspect, a tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to safety device operators; receiving assignment informationat the safety device when an NFC radio of the safety device is broughtin proximity to at least one of the plurality of NFC tags; andtriggering an activation of a function of the safety device based on thetemporary assignment information.

In an aspect, A tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to safety device operators; receiving assignment informationat the safety device when an NFC radio of the safety device is broughtin proximity to at least one of the plurality of NFC tags; andtriggering a modification of a setting of the safety device based on thetemporary assignment information.

In an aspect, a tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to safety device operators; receiving assignment informationat the safety device when an NFC radio of the safety device is broughtin proximity to at least one of the plurality of NFC tags; triggeringone or more of an alarm and a message upon detection of a safety event,wherein the triggered alarm or message is filtered by the temporaryassignment information; and communicating the triggered alarm or messageto at least one other safety device in a mesh network with features asdescribed herein for presentation on the second safety device. Theassignment tags for identifying individuals are programmed withinformation including one or more of a name, a size, a weight, a typicalwork location, a job function, a typical instrument used, a pre-existingconcern, a language known, a prior alarm, a prior gas event, a priorsafety event, and a prior message. The assignment tags for identifyinglocations are programmed with information including one or more of alocation within a space, a GPS location, an equipment at the location, afuel source at the location, a known hazard at the location, a typicalgas concentration for the location, an environmental condition for thelocation, a recent gas event, a recent man down alarm, a recent alarm,and a recent message. Triggering further comprises applying a filterbased on the assignment tag's programmed information. The safety deviceis at least one of a multi-gas detection instrument and a gas detectioninstrument. The safety device is at least one of a respirator, aharness, a lighting device, a fall arrest device, a thermal detector, aflame detector, and a chemical, biological, radiological, nuclear, andexplosives (CBRNE) detector. The safety event is a gas event.

In an aspect, a tangible article of manufacture having instructionsstored thereon that, when executed, causes a machine to performoperations for tracking an operator and operator status using a safetydevice, the operations comprising: programming a plurality of NFC tagswith assignment information, wherein the assignment information is atleast one of a location assignment for NFC tags being placed atparticular locations and an instrument operator assignment for tagsdistributed to safety device operators; receiving assignment informationat the safety device when an NFC radio of the safety device is broughtin proximity to at least one of the plurality of NFC tags; triggering amodification of a setting of the safety device based on the temporaryassignment information; and communicating the modified setting to atleast one other safety device in a mesh network with features asdescribed herein for modification of a setting of the second safetydevice.

In an aspect, an alerting system includes a safety device comprising aGPS system; and an interface configured to: transmit the location of thesafety device based on data from the GPS system to a remote server;receive alert information from the remote server in response to theremote server determining the location of the safety device correspondsto a hazardous location, wherein the remote server determines thehazardous location based on a condition detected from one or more of thesafety device, a second safety device in an area within a pre-defineddistance from the safety device, an area monitor, and third party data;and communicate the alert information to one or more devices in a meshnetwork with features as described herein joined by the safety device.The interface is a component of the safety device, a network gateway, ora smart phone.

In an aspect, an alerting system includes a safety device configured toread at least one of a plurality of location NFC tags comprisinginformation regarding the location in which it is placed; and aninterface configured to: transmit the location of the safety devicebased on the information from the location NFC tag to a remote server;and receive alert information from the remote server in response to theremote server determining the location of the safety device correspondsto a hazardous location, wherein the remote server determines thehazardous location based on a condition detected from one or more of thesafety device, a second safety device in the location, an area monitorin the location, and third party data related to the location. Theinterface is a component of the safety device, a network gateway, or asmart phone. The interface is further configured to communicate thealert information to one or more devices in a mesh network joined by thesafety device.

In an aspect, a computer-implemented method for providing real timelocating and gas exposure monitoring includes receiving, by a computerprocessor, a first gas reading and a first location from a first device;receiving, by the computer processor, a second location from a seconddevice; and transmitting one or more of an alert and the gas reading tothe second device when the second location is within a predetermineddistance from the first location and the gas reading exceeds athreshold, wherein the second device relays the alert and/or the gasreading to at least one peer device in a mesh network with features asdescribed herein joined by the second device.

In an aspect, a computer-implemented method for providing real timelocating and gas exposure monitoring includes receiving, by a computerprocessor, a first gas reading and a first location from a first device,wherein the first location is read from a location NFC tag in thelocation by the first device; receiving, by the computer processor, asecond location from a second device; and transmitting one or more of analert and the gas reading to the second device when the second locationis within a predetermined distance from the first location and the gasreading exceeds a threshold. The second device relays the alert and/orthe gas reading to at least one peer device in a mesh network withfeatures as described herein joined by the second device.

In an aspect, a computer-implemented method for providing real timelocating and gas exposure monitoring includes receiving, by a computerprocessor, a first safety event and a first location from a firstdevice; receiving, by the computer processor, a second location from asecond device; and transmitting an alert and the safety event to thesecond device when the second location is within a predetermineddistance from the first location, wherein the second device relays thealert and/or the gas reading to at least one peer device in a meshnetwork with features as described herein joined by the second device.

In an aspect, a computer-implemented method for providing real timelocating and gas exposure monitoring includes receiving, by a computerprocessor, a first safety event and a first location from a firstdevice, wherein the first location is read from a location NFC tag inthe location by the first device; receiving, by the computer processor,a second location from a second device; and transmitting an alert andthe safety event to the second device when the second location is withina predetermined distance from the first location. The second devicerelays the alert and/or the gas reading to at least one peer device in amesh network with features as described herein joined by the seconddevice.

In an aspect, a system includes a plurality of portable environmentalsensing devices in a work area adapted to communicate with one anotherin a mesh network with features as described herein; and acommunications facility to transmit data from at least one of theplurality of portable environmental sensing devices to a remotecomputer, the remote computer configured to monitor at least one of ahazardous condition and an activation of a panic button in the work areabased on data from the at least one of the plurality of portableenvironmental sensing devices, wherein the remote computer is configuredto: receive, from the at least one portable environmental sensingdevice, an alarm related to the hazardous condition or activation ofpanic button, and transmit to any of the portable environmental sensingdevices an instruction to be propagated throughout the mesh network. Theinstruction is a request to check the safety of a user of the at leastone portable environmental sensing device, an evacuation instruction, arisk mitigation instruction, or the like. The remote computer is furtherconfigured to display the location of the portable environmental sensingdevices in a map of the work area, wherein the remote computer transmitsthe map for display on the any of the portable environmental sensingdevices. The data is sensed gas data, wherein the hazardous condition isbased on the sensed gas data exceeding a threshold and the remotecomputer is further configured to display the sensed gas data in a mapof the work area. A size of the representation of the gas data isproportional to the gas level. The remote computer is further configuredto request an emergency response at the location of the at least oneportable environmental sensing device.

In an aspect, a system for providing an ad-hoc mesh network withfeatures as described herein for an eyewash station includes a sensordisposed within the eyewash station to monitor a condition, the sensoradapted to communicate with nodes in a mesh network; and a digital sign,wherein the digital sign is adapted to receive data related to thecondition from the sensor through the mesh network for presentation.

In an aspect, a system for providing an ad-hoc mesh network withfeatures as described herein for an eyewash station includes a sensordisposed within the eyewash station to monitor a condition, the sensoradapted to communicate with nodes in a mesh network; and a device in themesh network configured to receive the communication from the sensorrelated to the condition and generate an alarm based on the conditionmeeting a threshold or criteria. The system further includes a digitalsign in the mesh network, wherein the digital sign is adapted to receivethe alarm from the device through the mesh network for presentation. Thedevice in the mesh network is further configured to obtain one or moreof a worker biometric datum and an area environmental datum. The devicein the mesh network is further configured to transmit the alarm to aremote computer. The device in the mesh network is further configured toobtain an inventory of potential hazards from an NFC tag in the areanear the eyewash station when an NFC radio of the device is brought inproximity to the NFC tag. A secondary alarm is generated based on atleast one item in the inventory.

In an aspect, a method of sensing a root cause or symptom of death orinjury of a worker on a worksite includes obtaining sensor data from oneor more body worn sensors attached to the body of the worker, whereinthe sensor data relates to one or more physiological and behavioraleffects of the root cause of worker death or injury; analyzing thesensor data to identify a safety issue; and modifying an authorizationlevel of the worker when the analyzed sensor data identifies a presenceof the safety issue, wherein the authorization level is stored on adevice of the worker.

In an aspect, a method of sensing a root cause or symptom of death orinjury of a worker on a worksite includes obtaining sensor data from oneor more body worn sensors attached to the body of the worker, whereinthe sensor data relates to one or more physiological and behavioraleffects of the root cause of worker death or injury; analyzing thesensor data to identify a safety issue; and when the analyzed sensordata identifies a presence of the safety issue, communicating the safetyissue to a safety device of the worker for presentation on the safetydevice. The method further includes communicating the safety issue to asecond safety device of a second worker for presentation, wherein thesafety device and the second safety device are peers in a mesh network.

In an aspect, a method of sensing a root cause or symptom of death orinjury of a worker on a worksite includes obtaining sensor data from oneor more body worn sensors attached to the body of the worker, whereinthe sensor data relates to one or more physiological and behavioraleffects of the root cause of worker death or injury; analyzing thesensor data to identify a safety issue; and when the analyzed sensordata identifies a presence of the safety issue, communicating a requestto check-in with the worker to a safety device of a second worker.

In an aspect, a system for providing a low-power ad-hoc mesh networkwith features as described herein for a remote jobsite includes aplurality of network devices comprising one or more worker monitoringdevices and one or more area monitoring devices, wherein the networkdevices monitor at least one of a peer alarm, a worker biometric datumor an area environmental datum; and the network devices adapted tocommunicate with one another in a mesh network without a central networkcontroller; wherein a first network device of the plurality of networkdevices transmits the peer alarm, the worker biometric datum or the areaenvironmental datum to a second network device of the plurality ofnetwork devices for presentation on the second network device.

In an aspect, a system includes a plurality of network devicescomprising one or more worker monitoring devices and one or more areamonitoring devices, wherein the network devices monitor at least one ofa peer alarm, a worker biometric datum or an area environmental datum,the network devices adapted to communicate with one another in a meshnetwork with features as described herein; and a network gateway,wherein the plurality of network devices transmits the peer alarm, theworker biometric datum or the area environmental datum to a remotecomputer through the gateway.

In an aspect, a system includes a plurality of network devicescomprising one or more worker monitoring devices and one or more areamonitoring devices, wherein the network devices monitor at least one ofa peer alarm, a worker biometric datum or an area environmental datum,the network devices adapted to communicate with one another in a meshnetwork with features as described herein; and a device interface for aremote-networked device, wherein the plurality of network devicestransmits the peer alarm, the worker biometric datum or the areaenvironmental datum to the remote-networked device, wherein theremote-networked device is configured to further transmit the peeralarm, the worker biometric datum or the area environmental datum to aremote computer.

In an aspect, a method of sensing a root cause or symptom of death orinjury of a worker on a worksite includes obtaining sensor data from oneor more body worn sensors attached to the body of the worker, whereinthe sensor data relates to one or more physiological and behavioraleffects of the root cause of worker death or injury; analyzing thesensor data to identify a safety issue; and providing an alert to theworker or a third party when the analyzed sensor data identifies apresence of the safety issue. The alert is transmitted from the one ormore body-worn sensors to a remote location via a network connection.The alert is transmitted directly from the one or more body-worn sensorsto one or more workers located on the worksite. The step of analyzingthe sensor data occurs within the body worn sensor. The sensor data istransmitted via a wireless network from the body-worn sensor to a remotelocation for analysis of the sensor data. The remote locationcommunicates with the body-worn sensor to alert the worker wearing thebody-worn sensor when the analyzed sensor data identifies the presenceof the safety issue. The remote location communicates with the thirdparty on the worksite to alert the third party that the analyzed sensordata indicates the presence of the safety issue related to the workerwearing the body-worn sensor. The physiological effects include aneffect on at least one of ECG, heart rate, blood pressure, breathingrate, skin temperature, posture, activity, accelerometry, bloodpressure, pulse, body odors, blood alcohol level, glucose levels, andoxygen saturation. The behavioral effects include an effect on at leastone of gait, walking patterns, posture, eye movements, pupil size,motion patterns, noises, and removal of the sensor from the personbefore a prescribed time. The body-worn sensors comprise one or more ofa heart rate sensor, blood pressure sensor, gait detection sensor,olfactory sensor, galvanic skin response sensor, proximity sensor,accelerometer, eye tracking sensor, image sensor, microphone, infraredsensor, gas sensor, capacitive sensor, fingerprint sensor, networkingsignal detector, and location detector. The method further includes thestep of storing the sensor data and comparing current sensor data tostored sensor data to determine a variance indicating a safety issue.The method further includes the step of storing typical sensor data froma plurality of workers and comparing current sensor data for the workerto stored sensor data for the plurality of workers to determine avariance indicating a safety issue. The method further includes the stepof preventing the worker from accessing a system after identifying asafety issue. The method further includes the step of suggesting abehavior change to the worker to avoid a safety issue.

In an aspect, a system for providing a low-power ad-hoc mesh network fora remote jobsite includes a plurality of network devices comprising oneor more sensing devices and one or more area monitoring devices, whereinthe network devices monitor at least one of a peer alarm, a workerbiometric datum or an area environmental datum; the network devicesadapted to communicate with one another in a mesh network with featuresas described herein; wherein a first network device of the plurality ofnetwork devices transmits the peer alarm, the worker biometric datum orthe area environmental datum to a second network device of the pluralityof network devices for presentation on the second network device.

In an aspect, a network for connecting a plurality of network nodes withfeatures as described herein includes a leader node; and a plurality offollower nodes, wherein the leader node transmits a sync message to theplurality of follower nodes indicating a beginning of a networkinterval, wherein the leader node and the plurality of follower nodestransmit information during a transmission period of the networkinterval and do not transmit information during a sleep period of thenetwork interval, the leader node and plurality of follower nodes usingless power in the sleep period than the transmission period, theplurality of follower nodes each comprising a timer, the timer adaptedto time the transmission period and sleep period of a plurality offuture network intervals in an absence of continued receipt of the syncmessage from the leader node during the plurality of future networkintervals. When any of the plurality of follower nodes receive a syncmessage, the follower node transmits a message advertising one or moreproperties of the leader node during a predetermined period of thenetwork interval. The one or more properties of the leader node includesat least one of a channel hopping sequence and a total number of thenetwork nodes on the network. When any one of the plurality of followernodes fails to receive a receive a sync message from the leader node,the follower node refrains from transmitting a message advertising aproperty of the leader node during the network interval. Follower nodeseach comprise a counter for tracking the receipt of sync message fromthe leader. The counter is incremented when a sync message is receivedand decremented when a sync message is not received. When the counter ofany one of the follower nodes reaches a predetermined value, thefollower node initiates a procedure for finding a new leader node. Whenthe timer is further adapted to time an expected receipt of future syncmessages of future network intervals and when an actual receipt of thefuture sync message deviates from an expected receipt of the future syncmessage by a predetermined amount of time for a predetermined number ofnetwork intervals, the follower node adjusts the timer to more closelycorrespond with the actual receipt of the future sync message. The syncmessage includes data indicating the number of network nodes in thenetwork. The length of the transmission period is determined by thenumber of network nodes in the network. The network nodes areenvironmental sensing devices. The information is assigned by reading anNFC tag. The information relates to a concentration of gas or anenvironmental attribute. The network nodes are environmental sensingdevices, and the one or more properties is assigned by reading an NFCtag.

In an aspect, a network for connecting a plurality of network nodes withfeatures as described herein includes a leader node; and a plurality offollower nodes, wherein the leader node transmits a sync message to theplurality of follower nodes indicating a beginning of a networkinterval, wherein the leader node and the plurality of follower nodestransmit information during a transmission period and do not transmitinformation during a sleep period of the network interval, and whereinduring a predetermined time of the transmission period of the networkinterval each of the follower nodes that received the sync messagetransmit a message advertising one or more properties of the leadernode. The one or more properties of the leader node includes at leastone of a channel hopping sequence and a total number of the networknodes on the network. When any of the plurality of follower nodes failsto receive a receive a sync message from the leader node, the followernode refrains from transmitting a message advertising a property of theleader node during the network interval. The message advertising aproperty of the leader node is broadcast on a predetermined subset ofchannels. A new follower node attempting to join the network listens onthe predetermined subset of channels to receive the message advertisingat least one property of the leader node to learn the at least oneproperty of the leader node to facilitate the new follower node to jointhe network. At least one property comprises the total number of networknodes already on the network and the new follower node will refrain fromattempting to join the network when the total number of network nodesexceeds a predetermined value. After a predetermined interval, theleader node refrains from sending the sync message and entering thesleep period for at least one network interval and listens for messagesadvertising at least one property of a different leader node. The leadernode is a gas sensor. If the leader node receives a message advertisingat least one property of the different leader node, the leader nodestarts a process to cease performing as the leader node and beginperforming as a follower node of the different leader node. If theleader node does not receive a message advertising at least one propertyof another leader node, the leader node continues to perform as theleader node. The leader node and plurality of follower nodes use lesspower in the sleep period than the transmission period, the plurality offollower nodes each comprising a timer, the timer adapted to time thetransmission period and sleep period of a plurality of future networkintervals in an absence of continued receipt of the sync message fromthe leader node during the plurality of future network intervals. Whenthe follower nodes transmit the message advertising the one or moreproperties of the leader node, the message is transmitted with a singlehop such that a node receiving the message does not retransmit themessage.

In an aspect, a method of operating a wireless mesh network withfeatures as described herein includes the steps of: providing aplurality of nodes wherein each node is operable to perform as a leadernode or a follower node, wherein one node performs to identify itself asthe leader node and one or more other nodes operate as follower nodes;wherein the leader node transmits a sync message to follower nodesindicating a beginning of a network interval, wherein the leader nodeand the follower nodes transmit information during a transmission periodand do not transmit information during a sleep period of the networkinterval, and wherein during a predetermined time of the transmissionperiod of the network interval follower nodes that received the syncmessage transmit a message advertising one or more properties of theleader node. The one or more properties of the leader node includes atleast one of a channel hopping sequence and a total number of thenetwork nodes on the network. When any of the plurality of followernodes fails to receive a receive a sync message from the leader node,the follower node refrains from transmitting a message advertising aproperty of the leader node during the network interval. The messageadvertising a property of the leader node is broadcast on apredetermined subset of channels. A new follower node attempting to jointhe network listens on the predetermined subset of channels to receivethe message advertising at least one property of the leader node tolearn the at least one property of the leader node to facilitate the newfollower node to join the network. The at least one property comprisesthe total number of network nodes already on the network and the newfollower node will refrain from attempting to join the network when thetotal number of network nodes exceeds a predetermined value. After apredetermined interval, the leader node refrains from sending the syncmessage and entering the sleep period for at least one network intervaland listens for messages advertising at least one property of adifferent leader node. The leader node is a gas sensor. If the leadernode receives a message advertising at least one property of thedifferent leader node, the leader node starts a process to ceaseperforming as the leader node and begin performing as a follower node ofthe different leader node. If the leader node does not receive a messageadvertising at least one property of another leader node, the leadernode continues to perform as the leader node. The leader node andplurality of follower nodes use less power in the sleep period than thetransmission period, the plurality of follower nodes each comprising atimer, the timer adapted to time the transmission period and sleepperiod of a plurality of future network intervals in an absence ofcontinued receipt of the sync message from the leader node during theplurality of future network intervals. When the follower nodes transmitthe message advertising the one or more properties of the leader node,the message is transmitted with a single hop such that a node receivingthe message does not retransmit the message.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a first leader node; and aplurality of follower nodes, wherein the first leader node transmits async message to the plurality of follower nodes indicating a beginningof a network interval, wherein the plurality of follower nodes transmitinformation during a transmission period and do not transmit informationduring a sleep period of the network interval, and wherein during apredetermined time of the transmission period of the network intervaleach of the follower nodes that received the sync message transmit amessage advertising one or more properties of the first leader node; andwherein transmission period, the first leader nodes listens forinformation advertising one or more properties of a second leader node.The message advertising a property of the second leader node istransmitted on a predetermined channel. The first leader node listens onthe predetermined channel. The message advertising a property of thesecond leader node is also transmitted on a second predeterminedchannel. The first leader node also listens on the second predeterminedchannel. The first leader node listens for a period of time greater thanthe length of the network interval. When the first leader node receivesfor information advertising one or more properties of a second leadernode, the first leader node ceases performing as a leader node and isadapted to begin a sequence to join the second leader node as a followernode. The plurality of follower nodes are adapted to detect an absenceof the first leader node and begin a sequence to join a new leader node.The leader node and plurality of follower nodes use less power in thesleep period than the transmission period, the plurality of followernodes each comprising a timer, the timer adapted to time thetransmission period and sleep period of a plurality of future networkintervals in an absence of continued receipt of the sync message fromthe leader node during the plurality of future network intervals. Thenetwork nodes are environmental sensing devices. The information isassigned by reading an NFC tag. The information relates to aconcentration of gas. The information relates to an environmentalattribute. The one or more properties is assigned by reading an NFC tag.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits a sync message tothe plurality of follower nodes indicating a beginning of a networkinterval, wherein the plurality follower nodes each comprise a counterfor tracking the receipt of sync messages received from the leader nodeand the counter is incremented when a sync message is received anddecremented when a sync message is not received, wherein any of theplurality of follower nodes will begin a process of electing new leadernode when the counter decreases to a predetermined value. The leadernode and the plurality of follower nodes transmit information during atransmission period and do not transmit information during a sleepperiod of the network interval. The follower node whose counter hasdecremented to the predetermined value transmits a first nominatemessage to begin the process of electing a new leader node. The firstnominate message is transmitted on a predetermined channel. The firstnominate message is also transmitted on a second predetermined channel.The first nominate message includes data related to the suitability ofthe follower node sending the first nominate message to act as a leadernode. The data is calculated from a strength and reliability of signalsreceived from other network nodes on the network. The data is calculatedby utilizing at least one of an instrument type of the follower node, abattery state of charge, and past signal quality. The first nominatemessage and data are received by other network nodes and the datacompared by the receiving network nodes to data related to a suitabilityof the receiving network nodes to act as a leader node, wherein thereceiving network nodes reply with either a reply nominate message withdata indicating a higher suitability to act as a leader node or aconcede message if the receiving network node does not have a highersuitability to act as a leader node. When the follower node sending thefirst nominate message receives only concede messages, that followernode assumes the role of leader node and advertises at least oneproperty of itself as a leader node for other network nodes to becomefollower nodes. When the follower node sending the first nominatemessage receives a nominate message with data indicating a highersuitability to act as a leader node, that follower node sends a concedemessage. The concede messages are transmitted on the predeterminedchannel. The concede messages are also transmitted on the secondpredetermined channel.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits sync message to theplurality of follower nodes indicating a beginning of successive networkintervals, wherein upon nonreceipt of a predetermined number of syncmessages by a follower node that follower node initiates a process ofelecting a new leader node by a sending a first nominate message thatincludes data related to the suitability of the follower node to act asa leader node. The plurality of follower nodes each comprise a counterfor tracking the receipt of sync messages received from the leader nodeand the counter is incremented when a sync message is received anddecremented when a sync message is not received, wherein any of theplurality of follower nodes will begin a process of electing new leadernode when the counter decreases to the predetermined value. The firstnominate message is transmitted on a predetermined channel. The firstnominate message is also transmitted on a second predetermined channel.The data is calculated from a strength and reliability of signalsreceived from other network nodes on the network. The data is calculatedby utilizing at least one of an instrument type of the follower node, abattery state of charge, and past signal quality. The first nominatemessage and data are received by other network nodes and the datacompared by the receiving network nodes to data related to a suitabilityof the receiving network nodes to act as a leader node, wherein thereceiving network nodes reply with either a reply nominate message withdata indicating a higher suitability to act as a leader node or aconcede message if the receiving network node does not have a highersuitability to act as a leader node. When the follower node sending thefirst nominate message receives only concede messages, that followernode assumes the role of leader node and advertises at least oneproperty of itself as a leader node for other network nodes to becomefollower nodes. When the follower node sending the first nominatemessage receives a nominate message with data indicating a highersuitability to act as a leader node, that follower node sends a concedemessage. The concede messages are transmitted on the predeterminedchannel. The concede messages are also transmitted on the secondpredetermined channel. The network nodes are environmental sensingdevices. The information is assigned to the node by reading an NFC tag.The information relates to a concentration of gas. The informationrelates to an environmental attribute. The network nodes areenvironmental sensing devices.

In an aspect, a method of providing information about a leader node to aplurality of follower nodes in a wireless mesh communication networkwith features as described herein comprising: designating the leadernode; designating the plurality of follower nodes; designating one ormore predetermined frequency ranges as a public channel; from the leadernode and during a plurality of network intervals having a predeterminedlength of time, transmitting a sync message at a beginning of eachnetwork interval to the plurality of follower nodes; and during eachnetwork interval in which a sync message is received by any one of thefollower nodes, transmitting from any of the plurality of follower nodereceiving a sync message, upon the least one public channel, a messageadvertising at least one property of the leader node after receipt ofthe sync message. The leader node also sends a message advertising atleast one property of the leader node in any network interval in which async message is transmitted. The method may further include providing anew follower node not yet configured to receive the sync message; withthe new follower node, listening to the public channel until the atleast one property of the leader node is broadcast; and from the atleast one property, causing the new follower node to configure itself tocommunicate with the leader node on the next network cycle to join thenetwork. The at least one property of the leader node comprises at leastone of frequency hop parameters and the total number of leader andfollower nodes on the network. The at least one property of the leadernode comprises frequency hop parameters comprising a multiplier, anintercept and a seed for linear congruent generator. The frequency hopparameters further comprise channel mask parameters definingpredetermined channels as either one of used and unused. The frequencyhop parameters further comprise a length of time for the networkinterval. The at least one property of the leader node comprises thetotal number of leader and follower nodes on the network and wherein thenew follower node will not attempt to join the network if the totalexceeds a predetermined value. The leader node and follower nodes areenvironmental sensing devices.

In an aspect, a method of joining a new device to a mesh wirelessnetwork with features as described herein comprising: providing a meshwireless network comprising a leader node and a plurality of followernodes; designating at least one predetermined frequency range as apublic channel; transmitting on the public channel informationadvertising at least one property of the leader node; with a new deviceto the mesh wireless network, listening on the public channel for theinformation transmitted advertising at least one property of the leadernode; configuring the new device to follow the leader device using theat least one advertised property describing the leader node; with thenew device to the mesh wireless network, receiving a sync messagetransmitted from the leader node; and requesting the leader node to jointhe mesh wireless network. The step of transmitting on the publicchannel information advertising at least one property of the leader nodeis performed by at least one of the follower nodes in response toreceipt of a sync message. The step of transmitting on the publicchannel information advertising at least one property of the leader nodeis performed by the leader node after transmission of a sync message.The at least one property of the leader node comprises at least one offrequency hop parameters and the total number of leader and followernodes on the network. The at least one property of the leader nodecomprises frequency hop parameters comprising a multiplier, an interceptand a seed for linear congruent generator. The frequency hop parametersfurther comprise channel mask parameters defining predetermined channelsas either one of used and unused. The frequency hop parameters furthercomprise a length of time for the network interval. The at least oneproperty of the leader node comprises the total number of leader andfollower nodes on the network and wherein the new follower node will notattempt to join the network if the total exceeds a predetermined value.

In an aspect, a method of joining a follower node to a leader node in awireless mesh communication network with features as described hereincomprising: designating the leader node; designating the plurality offollower nodes; designating one or more predetermined frequency rangesas a public channel; from the leader node and during a plurality ofnetwork intervals having a predetermined length of time, transmitting async message at a beginning of each network interval to the plurality offollower nodes; during each network interval in which a sync message isreceived by any one of the follower nodes, transmitting from any of theplurality of follower nodes receiving a sync message, upon the least onepublic channel, a message advertising at least one property of theleader node after receipt of the sync message; providing a new followernode not yet configured to receive the sync message; with the newfollower node, listening to the public channel until the at least oneproperty of the leader node is broadcast and received by the newfollower node; and from the at least one property, causing the newfollower node to configure itself to communicate with the leader node onthe next network cycle to join the network. The method further includesproviding a new follower node not yet configured to receive the syncmessage; with the new follower node, listening to the public channeluntil the at least one property of the leader node is broadcast; andfrom the at least one property, causing the new follower node toconfigure itself to communicate with the leader node on the next networkcycle to join the network. The at least one property of the leader nodecomprises at least one of frequency hop parameters and the total numberof leader and follower nodes on the network. The at least one propertyof the leader node comprises frequency hop parameters comprising amultiplier, an intercept and a seed for linear congruent generator. Thefrequency hop parameters further comprise channel mask parametersdefining predetermined channels as either one of used and unused. Thefrequency hop parameters further include a length of time for thenetwork interval. The at least one property of the leader node comprisesthe total number of leader and follower nodes on the network and whereinthe new follower node will not attempt to join the network if the totalexceeds a predetermined value. The leader node is an environmentalsensing device. The devices are environmental sensing devices. Theleader node and follower nodes are environmental sensing devices.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits a sync message tothe plurality of follower nodes indicating a beginning of a networkinterval, wherein the sync message contains data indicating the numberof network nodes in the network, wherein the leader node and theplurality of follower nodes transmit information during a transmissionperiod of the network interval and do not transmit information during asleep period of the network interval, wherein the network interval is ofa fixed length of time, the transmission period is of a variable lengthof time based upon the number of network nodes in the network, and thesleep period comprises remaining time of the network interval after thetransmission period. The transmit time is divided between a firsttransmit time for transmitting high priority data and a second transmittime for lower prior data. The first transmit time and the secondtransmit time are equal length periods of time. The leader node andplurality of follower nodes use less power in the sleep period than thetransmission period, the plurality of follower nodes each comprising atimer, the timer adapted to time the transmission period and sleepperiod of a plurality of future network intervals in an absence ofcontinued receipt of the sync message from the leader node during theplurality of future network intervals. When any of the plurality offollower nodes receive a sync message, the follower node transmits amessage advertising one or more properties of the leader node during apredetermined period of the network interval. The one or more propertiesof the leader node includes at least one of a channel hopping sequenceand a total number of the network nodes on the network. When the timeris further adapted to time an expected receipt of future sync messagesof future network intervals and when an actual receipt of the futuresync message deviates from an expected receipt of the future syncmessage by a predetermined amount of time for a predetermined number ofnetwork intervals, the follower node adjusts the timer to more closelycorrespond with the actual receipt of the future sync message. Thenetwork nodes are environmental sensing devices. The information isassigned to the node by reading an NFC tag. The information relates to aconcentration of gas. The information relates to an environmentalattribute.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits a successiveplurality of sync messages to the plurality of follower nodes indicatinga beginning of successive network intervals, wherein the leader node andthe plurality of follower nodes transmit information during atransmission period of each network interval and wherein the leader nodechanges a channel of the sync message in subsequent network intervalsaccording to a channel change schedule and wherein the plurality offollower nodes change a channel to receive the sync messages ofsuccessive network intervals according to the same channel changeschedule, and leader node does not change a channel of transmissionduring the transmission period of the network interval. The channelchange schedule changes the channel for each successive networkinterval. The channel change schedule changes the channel after aplurality of network intervals. The channel change schedule is changedaccording to a linear congruential generator. When any of the pluralityof follower nodes receive a sync message, the follower node transmits amessage advertising one or more properties of the channel changeschedule. The channel change schedule is changed according to a linearcongruential generator. The one or more properties of the channel changeschedule comprises a seed, a multiplier and an intercept for the linearcongruential generator. The channel change schedule further indicateschannels that are unavailable to broadcast the sync message. The channelchange schedule further indicates channels that are available tobroadcast the sync message. The network nodes are environmental sensingdevices. The information is assigned to the node by reading an NFC tag.The information relates to a concentration of gas. The informationrelates to an environmental attribute.

In an aspect, a static memory device comprising: an instrumentcomprising at least one of an environmental sensing device, a hazarddetection device, and an industrial safety device, the instrumentoperating in a first sleep cycle in which the instrument is generatingdata related to the instrument type; a wireless radio for sending andreceiving information on a wireless mesh network with features asdescribed herein, the radio operating a second sleep cycle differentfrom the first sleep cycle in at least one of period and phase; and ashared memory operatively connected to the instrument and the radio, theshared memory comprising static message memory comprising staticmessages related to the instrument; an outgoing memory portion thatreceives outgoing information from the instrument and transmits theoutgoing information to the radio for transmission on the wireless meshnetwork, an incoming memory portion that receives incoming informationfrom the radio and transmits the incoming information to instrument, theshared memory further comprising request and grant lines for the radioand for the instrument to allow the radio and the instrument to requestand grant data to the incoming memory or the outgoing memory, whereinthe shared memory is adapted to not allow the both the radio and theinstrument to raise the grant lines and grant data to either theincoming or the outgoing memory simultaneously. The device furtherincludes a radio internal buffer for providing additional memory spaceto the radio. The first and second sleep cycles differ in both periodand phase. The shared memory further comprises an urgent line thatprovides an indicator to the instrument or the radio that theinformation in outgoing or incoming memory portion should be accessedimmediately. The information is assigned to the node by reading an NFCtag. The information relates to a concentration of gas. The informationrelates to an environmental attribute.

In an aspect, a network for connecting a plurality of network nodescomprising: a static memory device comprising: an instrument comprisingat least one of an environmental sensing device, a hazard detectiondevice, and an industrial safety device, the instrument operating in afirst sleep cycle in which the instrument is generating data related tothe instrument type; a wireless radio for sending and receivinginformation on a wireless mesh network with features as describedherein, the radio operating a second sleep cycle different from thefirst sleep cycle in at least one of period and phase; and a sharedmemory operatively connected to the instrument and the radio, the sharedmemory comprising static message memory comprising static messagesrelated to the instrument; an outgoing memory portion that receivesoutgoing information from the instrument and transmits the outgoinginformation to the radio for transmission on the wireless mesh network,an incoming memory portion that receives incoming information from theradio and transmits the incoming information to instrument, the sharedmemory further comprising request and grant lines for the radio and forthe instrument to allow the radio and the instrument to request andgrant data to the incoming memory or the outgoing memory, wherein theshared memory is adapted to not allow the both the radio and theinstrument to raise the grant lines and grant data to either theincoming or the outgoing memory simultaneously; and a wireless meshnetwork communicating with the radio comprising: a leader node; and aplurality of follower nodes, wherein the leader node transmits a syncmessage to the plurality of follower nodes indicating a beginning of anetwork interval, wherein the leader node and the plurality of followernodes transmit information during a transmission period of the networkinterval and do not transmit information during a sleep period of thenetwork interval, the leader node and plurality of follower nodes usingless power in the sleep period than the transmission period, theplurality of follower nodes each comprising a timer, the timer adaptedto time the transmission period and sleep period of a plurality offuture network intervals in an absence of continued receipt of the syncmessage from the leader node during the plurality of future networkintervals. The network further includes a radio internal buffer forproviding additional memory space to the radio. The first and secondsleep cycles differ in both period and phase. The shared memory furthercomprises an urgent line that provides an indicator to the instrument orthe radio that the information in outgoing or incoming memory portionshould be accessed immediately. The information is assigned to the nodeby reading an NFC tag. The information relates to a concentration ofgas. The information relates to an environmental.

In an aspect, a mesh network device for connecting to, sending andreceiving information on a mesh wireless network with features asdescribed herein comprising: an instrument comprising at least one of anenvironmental sensing device, a hazard detection device, and anindustrial safety device, a radio for transmitting and receivinginformation on the mesh wireless network; and a display for presenting asignal quality indicator of a connection of the radio to other nodes ofthe mesh wireless network, the signal quality indicator derived from acombination of the received signal strength (RSS) and packet receiveratio (PRR) of all the instruments in the mesh wireless network. Theinstrument multiplies an RSS of a most recent message received from eachnode in the mesh network by the PRR, which is the ratio of packetsreceived from each device in the mesh wireless network to a number ofexpected packets from each respective device in the mesh wirelessnetwork. The RSS represents a most recent network hop taken by a packet.The PRR is a counter that begins at a predetermined number and isincremented and decremented when expected packets are received or notreceived, respectively. The increment and decrement values are 3 and 2,respectively. The signal quality indicator is based on the product ofRSS*PRR for each node, summed and divided by a number of nodes in thenetwork. An alarm sounds when the signal quality indicator drops below apredetermined level. The information is assigned to the node by readingan NFC tag. The information relates to a concentration of gas. Theinformation relates to an environmental attribute.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits a sync message tothe plurality of follower nodes indicating a beginning of a networkinterval, wherein the sync message contains data indicating the numberof network nodes in the network, wherein the leader node and theplurality of follower nodes transmit information during a transmissionperiod of the network interval and do not transmit information during asleep period of the network interval, wherein each of the plurality ofthe follower nodes randomly select an interval during the transmissionperiod to transmit data and without respect to a time selected by any ofthe other follower nodes. The time randomly selected is with referenceto beginning of the transmission period. The network interval is of afixed length of time, the transmission period is of a variable length oftime based upon the number of network nodes in the network, and thesleep period comprises remaining time of the network interval after thetransmission period. The transmission period is divided between a firsttransmit time for transmitting high priority data and a second transmittime for lower prior data and wherein the time randomly selected totransmit data is with reference to the beginning of the first transmittime and the second transmit time. The first transmit time and thesecond transmit time are equal length periods of time. The leader nodeand plurality of follower nodes use less power in the sleep period thanthe transmission period, the plurality of follower nodes each comprisinga timer, the timer adapted to time the transmission period and sleepperiod of a plurality of future network intervals in an absence ofcontinued receipt of the sync message from the leader node during theplurality of future network intervals. When any of the plurality offollower nodes receive a sync message, the follower node transmits amessage advertising one or more properties of the leader node during apredetermined period of the network interval. The one or more propertiesof the leader node includes at least one of a channel hopping sequenceand a total number of the network nodes on the network. When the timeris further adapted to time an expected receipt of future sync messagesof future network intervals and when an actual receipt of the futuresync message deviates from an expected receipt of the future syncmessage by a predetermined amount of time for a predetermined number ofnetwork intervals, the follower node adjusts the timer to more closelycorrespond with the actual receipt of the future sync message. Thenetwork nodes are environmental sensing devices. The information isassigned to the node by reading an NFC tag. The information relates to aconcentration of gas. The information relates to an environmentalattribute.

In an aspect, a network with features as described herein for connectinga plurality of network nodes comprising: a leader node; and a pluralityof follower nodes, wherein the leader node transmits a sync message tothe plurality of follower nodes indicating a beginning of a networkinterval, wherein the sync message contains data indicating the numberof network nodes in the network, wherein the leader node and theplurality of follower nodes transmit information during a transmissionperiod of the network interval and do not transmit information during asleep period of the network interval, wherein the transmission period isdivided between a first transmit time for transmitting high prioritydata and a second transmit time for transmitting lower prior data. Eachof the plurality of the follower nodes randomly select an intervalduring the transmission period to transmit data and without respect to atime selected by any of the other follower nodes and wherein the timerandomly selected to transmit data is with reference to the beginning ofthe first transmit time and the second transmit time. The networkinterval is of a fixed length of time, the transmission period is of avariable length of time based upon the number of network nodes in thenetwork, and the sleep period comprises remaining time of the networkinterval after the transmission period. The first transmit time and thesecond transmit time are equal length periods of time. The leader nodeand plurality of follower nodes use less power in the sleep period thanthe transmission period, the plurality of follower nodes each comprisinga timer, the timer adapted to time the transmission period and sleepperiod of a plurality of future network intervals in an absence ofcontinued receipt of the sync message from the leader node during theplurality of future network intervals. When any of the plurality offollower nodes receive a sync message, the follower node transmits amessage advertising one or more properties of the leader node during apredetermined period of the network interval. The one or more propertiesof the leader node includes at least one of a channel hopping sequenceand a total number of the network nodes on the network. When the timeris further adapted to time an expected receipt of future sync messagesof future network intervals and when an actual receipt of the futuresync message deviates from an expected receipt of the future syncmessage by a predetermined amount of time for a predetermined number ofnetwork intervals, the follower node adjusts the timer to more closelycorrespond with the actual receipt of the future sync message. Thenetwork nodes are environmental sensing devices. The information isassigned to the node by reading an NFC tag. The information relates to aconcentration of gas. The information relates to an environmentalattribute.

In an aspect, a catalytically activated combustible gas sensing elementmay include a filament of resistance wire forming a coil, wherein afirst end of the resistance wire is attached to a first support post anda second end of the resistance wire is attached to a second supportpost, a cantilever support supporting the coil, wherein the cantileversupport is attached to a third support post, and a catalytic beadsubstantially surrounding the coil and cantilever. The resistance wiremay be coated via chemical vapor deposition with an insulating materialpreventing winds of the coil from electrically conducting through anexterior surface of the wire. The cantilever support may be attached tothe resistance wire, such as by soldering. It may be attached to asingle coil of the resistance wire, to more than one but not all coilsof the resistance wire, or to all coils of the resistance wire. Thecantilever support may be disposed within, but does not contact theresistance wire. The cantilever support may be disposed below theresistance wire or above the resistance wire. The gas sensing elementmay further include a bead enveloping the cantilever support and theresistance wire. The bead may include a catalytic material, such as oneor both of platinum or palladium, or a ceramic material. The bead mayinclude an inner layer of a porous oxide-supported precious metalcatalyst and an outer layer of a porous oxide-supported catalyticmaterial.

In an aspect, a catalytically activated combustible gas sensing elementmay include a filament of resistance wire forming a coil, wherein theresistance wire is of a diameter equal to or less than 0.5 millimeters,wherein a first end of the resistance wire is attached to a firstsupport post and a second end of the resistance wire is attached to asecond support post; and a cantilever support adapted to support thecoil, wherein the cantilever support is attached to a third supportpost; wherein the resistance wire can withstand more than eight drops ofone meter onto concrete without breakage. The cantilever support isattached to the resistance wire. It may be attached to a single coil ofthe resistance wire, to more than one but not all coils of theresistance wire, or to all coils of the resistance wire. The cantileversupport may be disposed within, but does not contact the resistancewire. The cantilever support may be disposed below the resistance wireor above the resistance wire. The gas sensing element may furtherinclude a bead enveloping the cantilever support and the resistancewire. The bead may include a catalytic material, such as one or both ofplatinum or palladium, or a ceramic material. The bead may include aninner layer of a porous oxide-supported precious metal catalyst and anouter layer of a porous oxide-supported catalytic material.

In an aspect, a portable electrochemical gas sensing apparatus mayinclude a housing comprising an exterior surface that defines aninterior space, wherein at least one depression is formed in theexterior surface; an electrochemical gas sensor at least partiallydisposed within the at least one depression of the housing; and aprocessing unit disposed in the interior space of the housing and inelectrical communication with the electrochemical gas sensor. Thecomponents of the electrochemical gas sensor may include an electrodestack, wherein the electrode stack comprises at least one gas permeablemembrane, at least one electrolyte absorption pad, at least onemeasuring electrode, and at least one counter electrode. The at leastone depression may include a first reservoir, a second reservoir, and acentrally-disposed raised platform formed within the at least onedepression of the exterior surface, and the platform is shaped tosupport, at least in part, the electrode stack. The electrode stack mayrest on the raised platform and covers the second reservoir. The secondreservoir may be adapted to hold an electrolyte solution that is influid communication with the electrode stack. The electrode stack may bein electrical communication with an alarm modality, wherein the alarmmodality is disposed in the interior space of the housing. The alarmmodality is wirelessly connected to the processing unit. The apparatusmay further include a cap sized to fit over the at least one depression.The cap includes a capillary hole providing access for gas entry intothe electrode stack. The electrochemical sensor senses one or more of:oxygen, carbon monoxide, methane, and hydrogen sulfide. The interiorspace of the housing is sealed. The apparatus may further include apower source disposed in the interior space of the housing to power thealarm modality.

In an aspect, a portable combustible lower explosive limit (LEL) gassensing apparatus may include a housing comprising an exterior surfaceand that defines an interior space, wherein at least one depression isformed in the exterior surface; a combustible gas sensor at leastpartially disposed within the at least one depression of the housing;and a processing unit disposed in the interior space of the housing andin electrical communication with the combustible gas sensor. The atleast one depression holds at least one catalytic sensing bead in achamber. The at least one catalytic sensing bead is in electricalcommunication with components of the apparatus disposed in the interiorspace. The at least one depression includes two chambers with an chamberseparator integrally formed in the depression, wherein each chamber isadapted to hold at least one catalytic sensing bead. The apparatus mayfurther include a sensor flame arrestor that covers the at least onedepression. The apparatus may include a gas sensing element including anelectric heating element, a first layer coated on the electric heatingelement and comprising a precious metal catalyst supported on a porousoxide, the precious metal catalyst catalyzing combustion of acombustible gas to be detected by the sensing element, and a secondlayer overlaying the first layer, and comprising a catalytic compoundcapable of trapping gases that poison the precious metal catalyst, saidcatalytic compound being supported on a porous oxide; a compensatingelement comprising an electric heating element, said compensatingelement not including a catalyst capable of catalyzing combustion of acombustible gas to be detected by the sensing element; and a processingunit to which the sensing element and compensating element areconnected, the processing unit being constructed and arranged to detectchanges in resistance of the sensing element and compensating element,and to provide a reading of said changes. The catalytic materials forthe first and second layers may include one or more of oxide-supportedmetal oxides supported on porous oxide supports, solid acids, solidbases, and metal-loaded zeolites and clays. The apparatus may furtherinclude at least one reference electrode.

In an aspect, a circuit for tuning an unbalanced Wheatstone bridgecircuit in a combustible catalytic gas sensor to minimize baselinevoltage drift may include a first branch comprising a sensor bead inseries with a compensating bead wherein the temperature and resistanceof the sensing bead increases in comparison to the compensating beadwhen in the presence of a combustible gas, a second branch, connected inparallel with the first branch, comprising two resistors; a meter tomeasure a baseline voltage differential between the two branchesconnected between the beads on the first branch and between the tworesistors on the second branch; and one or more variable resistor inparallel with each of or both of the sensor bead and the compensatingbead; wherein the one or more variable resistors may be adjusted tomaintain the baseline voltage differential as indicated by the meter atabout zero volts. The one or more variable resistor in parallel witheach of or both of the sensor bead and the compensating bead may includea variable resistor in parallel with the sensing bead and a variableresistor in parallel with the compensating bead. The one or morevariable resistor in parallel with each of or both of the sensor beadand the compensating bead may include a variable resistor in parallelwith sensing bead. The one or more variable resistor in parallel witheach of or both of the sensor bead and the compensating bead consists ofa variable resistor in parallel with the compensating bead.

In an aspect, a circuit for tuning an unbalanced Wheatstone bridgecircuit in a combustible catalytic gas sensor to minimize baselinevoltage drift including a first branch may include a sensor bead inseries with a compensating bead wherein the temperature and resistanceof the sensing bead increases in comparison to the compensating beadwhen in the presence of a combustible gas, a second branch, connected inparallel with the first branch, comprising a first and a secondresistance; a meter to measure a baseline voltage differential betweenthe two branches connected between the beads on the first branch andbetween the two resistors on the second branch; and wherein the firstresistance comprises one of a variable resistor or a fixed resistor inparallel with a variable resistor; and wherein the second resistancecomprises one of a variable resistor or a fixed resistor in parallelwith a variable resistor, but wherein the first resistance or secondresistance comprises at least one variable resistor; wherein the atleast one variable resistor may be adjusted to maintain the baselinevoltage differential as indicated by the meter at about zero volts. Thefirst resistance may include a fixed resistor. The first resistance mayinclude a fixed resistor in parallel with a variable resistor. Thesecond resistance may include a variable resistor. The second resistancemay include a fixed resistor in parallel with a variable resistor.

In an aspect, a circuit for tuning an unbalanced Wheatstone bridgecircuit in a combustible catalytic gas sensor to minimize baselinevoltage drift may include a first branch comprising a sensor bead inseries with a compensating bead wherein the temperature and resistanceof the sensing bead increases in comparison to the compensating beadwhen in the presence of a combustible gas, a second branch comprising apotentiometer comprising a first and a second leg having a first andsecond resistance, respectively, the first resistance in parallel withthe sensor bead and the second resistance in parallel with thecompensating bead; and a meter to measure a baseline voltagedifferential between the two branches connected between the beads on thefirst branch and between the first and second leg of the potentiometer;wherein the potentiometer is adjusted to maintain the baseline voltagedifferential as indicated by the meter at about zero volts. The circuitmay further include one or both of a primary resistor in parallel withthe first leg of the potentiometer and a secondary resistor in parallelwith the second leg of the potentiometer. The circuit may furtherinclude one or both of a primary resistor in series with the first legof the potentiometer and a secondary resistor in series with the secondleg of the potentiometer. The circuit may further include amicroprocessor, wherein the meter comprises an analog to digitalconvertor for providing the baseline voltage differential between thetwo branches to the microprocessor and potentiometer comprises adigitally controlled potentiometer controlled by the microprocessor forvarying the first and second resistances of the first and second legs ofthe digital potentiometer.

In an aspect, a process for manufacturing a hydrogen sulfide filter foruse with a catalytic bead gas sensor may include preparing a solution ofa copper compound; applying the solution of copper compound to a glassfiber paper; drying the glass fiber paper; preparing a solution ofsodium borohydride; applying the solution of sodium borohydride to thecopper compound on the glass fiber paper; and drying the glass fiberpaper. The copper compound is one of copper chloride and copper sulfate.

In an aspect, a process for manufacturing a hydrogen sulfide filter foruse with a catalytic bead gas sensor may include preparing a solution ofa copper compound; applying the solution of the copper compound to aglass fiber paper; drying the glass fiber paper; and applying hydrogenin nitrogen to the glass fiber paper. The copper compound is one ofcopper chloride and copper sulfate.

In an aspect, a process for manufacturing a hydrogen sulfide filter foruse with a catalytic bead gas sensor may include preparing a solution ofa copper compound; preparing a solution of sodium borohydride; mixingthe solutions of the copper compound and sodium borohydride; and dryingthe resulting metallic copper particles. The copper compound is one ofcopper chloride and copper sulfate.

In an aspect, a filter for use with a catalytic bead sensor may includeparticulate metallic copper, wherein the sizes of the metallic copperparticles are predominantly between 1 nm and 100 nm and a substrate tosupport the particulate metal copper. The substrate may include at leastone of glass fiber paper, alumina, silica, zirconia, and titanium. Thesubstrate may be coated with the particulate metal copper.

In an aspect, a filter for use with a catalytic bead sensor may includean assembly of particulate metallic copper dried to form a shapesuitable for use as a filter, wherein the sizes of the metallic copperparticles are predominantly between 1 nm and 100 nm.

In an aspect, a hydrogen sulfide filter for use with a catalytic beadsensor may include a metal not comprising lead wherein the sensorsensitivity to methane remains above 0.65 mV/% LEL for greater than20,000 seconds. The metal may include a metallic copper.

In an aspect, a hydrogen sulfide filter for use with a catalytic beadsensor may include a metal not comprising lead wherein the sensorcapacity to hydrogen sulfide is greater than 550 parts per millionhours. The metal may include a metallic copper. The sensor capacity tohydrogen sulfide may be greater than 600 parts per million hours, 650parts per million hours, 700 parts per million hours, or 750 parts permillion hours.

In an aspect, a device for determining a heat index may include ahousing, which in embodiments may be adapted to be attached to thehuman, the housing including a temperature sensor; a humidity sensor; amicroprocessor in communication with the temperature sensor and thehumidity sensor; and at least two microphones, the microphones arrangedto provide a first and second signal, respectively, to themicroprocessor for determining an estimated wind speed; wherein themicroprocessor, based upon data communicated from the temperature sensorand the humidity sensor and from the estimated wind speed, is configuredto calculate a heat index and wherein the microprocessor provides anotification signal to alert when the heat index is determined to beexcessive. The device includes at least three microphones. Thetemperature sensor, humidity sensor and microphones may all besolid-state. The housing further includes or the device is at least oneof a portable or area environmental sensing device, a portable or areagas sensor, a portable or area multi-gas detection instrument, arespirator, a lighting device, a fall arrest device, a thermal detector,a flame detector, and a chemical, biological, radiological, nuclear, andexplosives (CBRNE) detector. The housing further includes anelectrochemical gas sensor at least partially disposed within thehousing comprising an electrode stack, wherein the electrode stackcomprises at least one gas permeable membrane, at least one electrolyteabsorption pad, at least one measuring electrode, at least one counterelectrode, and at least one reference electrode, the circuit incommunication with the microprocessor to provide a signal related to thepresence of one or more particular gases and the microprocessor adaptedto provide an alarm related to an excessive level of one or more of theparticular gases. The housing further includes a combustible gas sensorat least partially disposed within the housing comprising at least onecatalytic sensing bead in a chamber, the combustible gas sensor incommunication with the microprocessor to provide a signal related to thepresence of one or more combustible gases and the microprocessor adaptedto provide an alarm related to an excessive level of the one or morecombustible gases. The wind speed is at least one of a maximum windspeed, an instantaneous wind speed, and an average wind speed. The alertis an audible alarm to the human based on the calculated heat index. Thealert is an electronic communication transmitted to a remote locationbased on the calculated heat index.

In an aspect, a method of protecting a human or device from exposure toexcessive heat may include providing a housing, optionally adapted to beattached to the human, the housing including a temperature sensor; ahumidity sensor; at least two microphones; and a microprocessor; withthe microprocessor calculating a wind speed from a signal received fromthe at least two microphones; with the microprocessor calculating a heatindex based upon data received from the temperature sensor, humiditysensor and from the wind speed; and providing an alert when thecalculated heat index is determined to be excessive. The at least twomicrophones include at least three microphones. The temperature sensor,humidity sensor and microphones may all be solid-state. Themicroprocessor may further be electrically connected to one of aportable or area environmental sensing device, a portable or area gassensor, a portable or area multi-gas detection instrument, a respirator,a lighting device, a fall arrest device, a thermal detector, a flamedetector, and a chemical, biological, radiological, nuclear, andexplosives (CBRNE) detector. The method may further include the stepsof: providing an electrochemical gas sensor at least partially disposedwithin the housing comprising an electrode stack, wherein the electrodestack comprises at least one gas permeable membrane, at least oneelectrolyte absorption pad, at least one measuring electrode, at leastone counter electrode, and at least one reference electrode; providing asignal from the electrochemical gas sensor to the microprocessor relatedto the presence of one or more particular gases; and with themicroprocessor, providing an alarm signal when the signal from theelectrochemical gas sensor indicates an excessive level of one or moreof the particular gases. The method may further include the steps of:providing a combustible gas sensor at least partial disposed within thehousing comprising at least one catalytic sensing bead in a chamber,providing a signal from the combustible gas sensor to the microprocessorrelated to the presence of one or more combustible gases; and with themicroprocessor, providing an alarm signal when from the combustible gassensor indicates an excessive level of one or more combustible gases.The wind speed is at least one of a maximum wind speed, an instantaneouswind speed, and an average wind speed. The alert is an audible alarm tothe human based on the calculated heat index. The alert is an electroniccommunication transmitted to a remote location based on the calculatedheat index.

These and other systems, methods, objects, features, and advantages ofthe present disclosure will be apparent to those skilled in the art fromthe following detailed description of the preferred embodiment and thedrawings.

All documents mentioned herein are hereby incorporated in their entiretyby reference. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure and the following detailed description of certainembodiments thereof may be understood by reference to the followingfigures:

FIG. 1 depicts an overview of the worker safety system.

FIG. 2 depicts a challenging environment for networking.

FIG. 3 depicts a system for propagating an alarm in a mesh network.

FIG. 4 depicts frequency channel overlap.

FIG. 5 depicts a shared memory interface.

FIG. 6A depicts a list of instruments on a display.

FIG. 6B depicts a shadow gas display.

FIG. 7 depicts a script process for the wireless network.

FIG. 8 depicts a synchronization scheme and FIG. 8A depicts a method forchoosing a leader from members of a network.

FIG. 9 depicts a leader election process.

FIG. 10 depicts a sleep cycle process.

FIG. 11 depicts the wireless network mesh architecture.

FIG. 12 depicts how the hardware enabling wireless network-compatibilitycan be extended to a platform using gateways to the Internet.

FIG. 13 depicts the wireless network fitting in a 7-layer OSI Model.

FIG. 14 depicts a method of the disclosure.

FIG. 15 depicts a block diagram of an embodiment of the disclosure.

FIG. 16 depicts a method of providing safety alerts.

FIG. 17 is an exploded view of various components of an exemplary gassensing apparatus.

FIG. 18 is a cross-sectional view of an exemplary electrochemical gassensing apparatus.

FIG. 19 depicts the electrochemical sensing apparatus of FIG. 18 withoutan electrode stack.

FIG. 20 illustrates a cross-sectional view of an exemplary combustiblelower explosive limit sensing apparatus.

FIG. 21 depicts a system for estimating heat index incorporated intoexisting detection equipment.

FIGS. 22A-22C depict various configurations of a heat index estimationsystem connected to or incorporated into detection equipment.

FIG. 23 depicts a system for estimating heat index incorporating threemicrophones.

FIG. 24 depicts a Wheatstone bridge circuit.

FIG. 25 depicts a gas sensor's span reserve and its baseline change overtime.

FIGS. 26A-26C depict balanced bridge circuits.

FIG. 27A depicts a balanced bridge circuit.

FIG. 27B depicts the relationship between component value and baseline

FIG. 28A depicts a balanced bridge circuit.

FIG. 28B depicts the relationship between component value and baseline.

FIG. 29A depicts a balanced bridge circuit.

FIG. 29B depicts the relationship between component values and baseline.

FIG. 30A depicts a balanced bridge circuit.

FIG. 30B depicts the relationship between component value and baseline.

FIG. 31 depicts a balanced bridge circuit.

FIG. 32A depicts a balanced bridge circuit.

FIG. 32B depicts the relationship between component value and baseline.

FIG. 33 depicts a balanced bridge circuit.

FIG. 34 depicts a method for the production of a metallic copper filterfor hydrogen sulfide.

FIG. 35 depicts a method for the production of a metallic copper filterfor hydrogen sulfide.

FIG. 36 depicts a method for the production of a metallic copper filterfor hydrogen sulfide.

FIG. 37 shows a graph of the relative capacity of different filters.

FIG. 38 shows a graph of sensor sensitivity over time in a hydrogensulfide environment.

FIG. 39A depicts a three support post design of a gas sensing orcompensating element of a gas sensor, before bead fabrication, with acantilever placed through the center of a coated coil, and attached tothe third support post.

FIG. 39B depicts the coil resting on the cantilever.

FIG. 39C depicts the cantilever touching an inside surface of the coil.

FIG. 40 depicts a three support post design of a gas sensing orcompensating element of a gas sensor, after bead fabrication, the beadfabricated to coat both the cantilever support and the coil.

DETAILED DESCRIPTION

Referring to FIG. 1, in order to provide various services and monitoringin a real-time or near-real time fashion with respect to portableenvironmental sensing devices, hazard detection devices, and othersafety instruments and devices, instruments and devices is such a systemneed reliable methods communicate with each other and/or with a remotelocation, all while in a challenging environment. This disclosuredescribes various aspects of a worker safety system, general componentsof which are shown in FIG. 1. The disclosure describes variouscommunications strategies and technologies to enable variousapplications and services related to worker safety. In addition toshowing the general components of such a system, FIG. 1 and theaccompanying description provide an overview of the communicationapproaches and strategies, certain useful accessories, and variousapplications enabled by the worker safety system.

FIG. 1 illustrates certain portable environmental sensing devices 108and area monitors 110, but it should be noted that other safety devicesmay be used with the system such as, multi-gas detection instruments, agas detection instruments, a portable electrochemical gas sensingapparatuses, respirators, a harness, lighting devices, fall arrestdevices, thermal detectors, flame detectors, or a chemical, biological,radiological, nuclear, and explosives (CBRNE) detector. In embodiments,environmental sensing device may be as described in “VENTIS PRO” U.S.Pat. Nos. 9,000,910, 9,575,043, 6,338,266, 6,435,003, 6,888,467, and6,742,382, which are incorporated by reference herein in their entirety.In embodiments, area monitors such as described herein as well as inU.S. Patent Application Publication No. 2016/0209386, entitled MODULARGAS MONITORING SYSTEM and filed on Jan. 15, 2016, the disclosure ofwhich is incorporated herein by reference in its entirety. Throughoutthis disclosure, the terms environmental sensing devices (orinstruments) 108, area monitors 110, and it should be understood thatany of methods, systems, applications, interfaces, and the likedescribed herein may be used by any of the environmental sensing devices(or instruments) 108, and area monitors 110. In addition, the disclosuremay refer to environmental sensing devices and area monitorscollectively as “instruments”. In embodiments, the environmental sensingdevices 108 and area monitors 110 may communicate with one another usinga mobile ad hoc wireless network (MANET) 104. As used herein, the termMANET is a continuously self-configuring, infrastructure-less network ofmobile devices connected wirelessly. One such MANET that may beimplemented is a mesh network. As used herein a mesh network is anetwork topology in which each node relays data for the network and allmesh nodes cooperate in the distribution of data in the network.Embodiments of the mesh network between environmental sensing devices108 and area monitors 110 will be described further herein. Inembodiments, the mesh network can enable communication betweencomponents of the system without the need of other conventionalcommunications technology for wireless communication, such as WiFi,satellite, or cellular technologies. Because the mesh wireless networkovercomes the challenge of operating a computer network where devicescommunication solely with a centralized device, such as a hub, switch orrouter, the network better operates in challenging environments whereobstructions or distance prevent wireless communication from a device toa hub. By utilizing the mesh network, devices can communicate with oneanother to transmit messages from devices to other devices tocommunicate with one another or to pass information among devices or toeventually transmit the message to a device on the perimeter of thenetwork for forwarding to another network, such as a device in thecloud. Industrial environments also typically represent challengingenvironments because sensors may be constantly moving or regularlychanging location, the environment can be large or remote from publicwireless infrastructure, large obstruction such as metal tanks may blocksignals, and the environment may be underground. This disclosure mayalso include devices, nodes, and the like communicating on apeer-to-peer network (P2P), which may be part of a mesh network. Itshould be understood that the embodiments described herein may operateon a mesh network, P2P network, or similar type of network. FIG. 1 alsodepicts various approaches to ultimately communicate data from theinstruments to the cloud or remote server, such as via an API 114, smartdevice 118 or other mobile gateway 131, a gateway 112, and a dock 122.

In embodiments, the mesh network 104 of this disclosure delivers “readyto use” wireless functionality to instrument platforms. When equippedwith hardware to be compatible with the mesh network 104 and embeddedfirmware, instruments are able to communicate wirelessly with oneanother. Mesh wireless networking provides instrument features such aspeer alarms, or “shadowing” readings from one instrument on anotherinstrument's screen—all within challenging environments typical toindustrial safety. The mesh networking feature set is available for areamonitors and portable instruments and enables interoperability, allowinga mixed network of portable and area monitor instruments to sharereadings and alarms.

Instruments 108 also communicate, via the mesh network with other meshnetwork-enabled infrastructure devices that further enable livemonitoring, automated messaging, and location awareness, such other meshnetwork-enabled infrastructure devices including network gateway device(also referred to herein as “gateway”) 112 and docks 122. For example, anetwork gateway device 112 may be placed in location in proximity toinstruments, devices, computers, vehicles, equipment, and the like toenable communication with a network infrastructure. The instruments maycommunicate with the network gateway device 112 through the mesh network104, and in embodiments, the data may be ultimately communicated, to acloud server, via networking technology, such as WiFi, cellular,satellite, and the like, for downstream uses, for example by a remoteserver as described herein. There may be two-way communication throughthe gateway 112 such that remote servers or applications running in thecloud may be used to control, configure or otherwise communicate withthe instruments 108, 110 through the gateway 112.

In embodiments, the dock 122, or docking station, may be used with theinstrument to provide predictive diagnostic information, as described inU.S. Pat. No. 6,442,639, entitled Docking Station for EnvironmentalMonitoring Instruments, which is incorporated by reference in itsentirety herein. The docking station or gateway 112 (or API 114/SmartDevice 118/mobile gateway 131 as described herein) may be connected,typically via the Internet, to a remote server 130, and exposure data,calibration data and diagnostic data are communicated from theinstrument to the docking station and from the docking station to theremote server 130. Mathematical analysis of the collected data from allavailable sources is performed by the remote server 130 to, among otherthings, generate predictive warnings to alert the users of potentialinstrument faults, thus allowing preemptive maintenance, incidentmanagement, and the like. The analysis methods include principlecomponent analysis and other statistical methods, fuzzy logic and neuralnetworks. In embodiments, the worker safety system can take data fromcomponents of the system, store such data, generate reports to be sortedbased on the data and communicate the data to a user. Such datacommunicated to a user can include, for example, events, need forcalibration/bump testing, maintenance record, alert that settings areincorrect or sub-optimal, and error codes. The remote server 130 mayalso generate alerts to send to users, can change settings remotely, canalert a user if another user has an alarm and provide information onwhere to respond, and other end use applications as described herein.

The mesh network may be tailored to the unique needs of worker-to-workercommunication. In an embodiment, the wireless network may be applied tothe challenge of hazardous gas detection—relaying alarms and readingsamong a group of gas detection instruments in the challengingenvironments described herein. Referring to FIG. 2, a particularchallenging environment is shown. Instruments 108 and 110 communicatewith a beacon 102, a tag 132, a wearable 134 and to a gateway 112through an external cellular, satellite, or WiFi network 136 to thecloud 138. A large metal tank 140 is present in the environment thoughwhich signals will not pass. FIG. 2 illustrates that instruments 108 and110 either communicate with nearby instruments 108 and/or 110 and notwith remote instruments or instruments blocked by obstructions, such astank 200. Instruments 108 and 110 interoperate to create paths for databetween instruments 108 and 110 which are not directly connected.

True mesh communications allowing sensors to communicate directly withone another is novel in portable gas detection. Daisy-chain alarms, suchas perimeter or fence line, for area monitoring exist, but currentwireless implementations for portable devices 108 only relay informationto a central display or “controller”, such as a laptop computer or adedicated display device.

This disclosure describes the features of the wireless network, and howthese features work in concert to address the challenges ofworker-to-worker communications. These challenges include ease of use,difficult environment, dynamic network topologies, and powerconsumption.

The mesh wireless network 104 may relay an alarm notification from oneinstrument to another instrument. “Peers” could be, for example, twoportable instruments worn by two members of a crew, three area monitorssurrounding a work zone, or some combination thereof. Peers are equalsin the network and information may be exchanged in both directions.

Points in a network are called nodes. Nodes in the mesh wireless network104 may include instruments 108, 110, devices 118, beacons 102 (whichare described further herein), gateways 131, 112, docks 122, and thelike. Most wireless networks have a coordinator node, a single entity inthe network to coordinate the activities of others. In star networktopologies such as WiFi, the coordinator node is the access point. InBluetooth, the coordinator node is the master (smartphone or PC). Inother mesh protocols like Zigbee and WirelessHART, a dedicatedcoordinator node is used. ZigBee is a registered trademark of PhilipsElectronics North American Corporation. WirelessHART is a registeredtrademark of Hart Communication Foundation. In all of these cases, thecoordinator role is necessary for the network to operate and is adedicated device for performing the coordinator function. Thecoordinator manages routing tables, sets Time Division Multiple Access(TDMA) slots, coordinates frequency hopping, etc. The coordinator may beline-powered for reliability and availability for communication. Forexample, in WirelessHART, the role of the coordinator is vital, a backupcoordinator is held in reserve, just in case the primary coordinatorfails.

A coordinator node is not required with the mesh wireless network 104 ofthe present invention, as it is a truly ad-hoc network. Any collectionof two or more instruments may form a network, without the need for anyinfrastructure. The mesh network 104 can tolerate the loss of anymember, at any time, without warning because each device communicateswith all other devices within range and maintains a database of devicesfrom whom communications have been received. When messages from a devicehave not been received within a predetermined period of time, the deviceis removed from the database.

For security, every node has a default private encryption key which maybe changed. By changing the encryption key, a network can be kept securebut also can be altered to keep mesh networks intended to operateseparately in the same space from communicating with one another, suchas keeping the network of different contractors in an industrialenvironment from contacting one another. The network is blind to nodesoperating on a different encryption key. Also for security, dynamicfrequency hopping, as described below, is implemented so that thechannel on which the network will be communicating is pseudo-random andconstantly changes. Finally, security may be implemented by bringing anode into contact or near-contact with a near field communication device(“NFC”) to identify and authorize that node on the network, as describedbelow.

High bandwidth, low latency MANETs, like those used on the battlefield,are extremely sophisticated. They involve multi-radio units andsignificant communications processing hardware, but wirelessenvironmental sensing such as gas detection may not require this levelof performance. The mesh network 104 excels at sharing a small amount ofinformation, with a plurality of other instruments, with relatively low(such as a few seconds) delay without the complexity of existinghigh-bandwidth, low latency MANETs. One feature eliminating thecomplexity of other MANETs is that the mesh network 104 assumes messagesreach their destination

In embodiments, the mesh network 104 emphasizes energy efficiency usingpower-efficient broadcasts of information. The network 104 operates on aconstant network interval, for example 1 second. Within the networkinterval is a period of broadcasting and a period of sleep cycling.Moreover, the length of the period of broadcasting is altered in themesh network 104 based upon the number of devices currently joined tothe network, such that a network with few devices can be even more powerefficient by increasing the period of sleep cycling within each networkinterval, as further described below.

In embodiments, the mesh network 104 may not be a long-range link. Themesh network 104 may typically operate at distances of 100-200 m betweenindividual nodes, and is not intended for remote monitoring of a distantsite. The mesh network 104 feature set is meant to communicate between,and alert workers within, the same group and working in the samevicinity. It provides acceptable range and coverage by leveraging themesh topology.

The mesh network 104 shares information and alarms with otherinstruments without a dedicated coordinator node, or any fixed nodes forthat matter.

In embodiments, the mesh network 104 provides a setting-free,self-forming, self-healing, resilient wireless network without adedicated coordinator node. As described below, there are no usersettings required, no channel selection, and no PAN id to enter. In oneembodiment, with the intuitive action of touching two instrumentstogether, a network may be formed. Touching another instrument to anexisting member of a network joins the new instrument into the networkif the instrument is not already in a network itself. Touching theinstruments may be a tap, double tap, bump, both being shaken together,a touch of the tops of the instruments, a touch of the bottoms of theinstruments, and the like. In embodiments, if when the instruments aretapped it is determined that they are each already members of adifferent network, each instrument may be prompted to leave theirnetwork, and if one leaves, upon re-tapping, the network joining may besuccessful. In a distributed fashion, the network is maintained andadapts as member instruments come and go and move about the challengingRF environment typical of industrial settings.

The wireless network's adaptability and resilience is a result of anemphasis on wireless diversity. This diversity takes three forms: spacediversity, frequency diversity, and time diversity. Space diversityinvolves transmitting a wireless signal over several differentpropagation paths, with the understanding that different pathsexperience radically different RF impediments. Space diversity is thereason most WiFi access points have more than one antenna—evenseparating two antennas by a few inches significantly reduces “deadspots” in coverage caused by reflections off walls and other objects.Instruments operating on the mesh network 104 are too small to benefitfrom multiple antennas; however a mesh network such as 104, wheremessages can take alternate paths through a network provides the sameeffect, even with as few as three nodes—as illustrated by the exampleabove.

Frequency diversity, also known as frequency hopping, is a scheme wherea communication system regularly changes the frequency (channel) usedfor communications. Frequency diversity helps overcome some sources ofdead zones because areas of destructive interference due to RFreflections (called multi-path fading or multi-path interference) occurat different locations at different frequencies. Frequency diversityalso helps avoid interference with other users of the wireless spectrum.If a nearby device is using only a portion of the spectrum, only sometransmissions are impacted. In embodiments, the mesh network 104 mayimplement a slow-hopping scheme. Each network interval (for example,about once per second), the network may switch frequencies, preferablyusing a pseudorandom sequence. This is in comparison to a “fast-hopping”system like Bluetooth, which changes frequencies 1,600 times per second.Fast-hopping is appropriate when an interruption of just millisecondswould matter—like streaming audio from a phone to a stereo. Slow hoppingrequires less computational horsepower (saving power) and simplifies theprocess of locating and joining networks.

Time diversity involves transmitting the same information at differentinstances of time. The chances of a message getting blocked multipletimes is far lower than if the message is sent just once. In the meshnetwork 104, time diversity may be achieved by at least two means.First, instruments on the mesh network 104 may transmit theirinformation quite often—at least once every few seconds. Second, eachregular transmission from an instrument on the mesh network 104 may be acomplete (yet compact) snapshot of the instrument's current condition(called state-based communications). For example, an instrument on thenetwork 104 may be a gas sensor which transmits its current state to thenetwork, including information identifying it as a gas sensor, a gasreading, an alarm status, whether a panic between has been pressed,instrument status, etc. In embodiments, nothing important is sent justonce (event-based communication), for example in a gas sensor thesnapshot of the devices current condition may be sent every networkcycle, for example. If one transmission is lost, for example due to acollision with another instrument's transmission, the next message islikely to make it through. Time diversity is particularly effective whencombined with frequency diversity, as the next transmission will use adifferent part of the RF spectrum that has different RF impediments.

In embodiments utilizing mesh networking, which is a collection ofwireless nodes that communicate with each other either directly orthrough one or more intermediate nodes, the nodes may operate inharmony, cooperatively passing information from point A to point B bymaking forwarding (routing) decisions based on their knowledge of thenetwork. Through this collaboration, a mesh network can extend over longdistances and operate in spite of very poor RF “line of sight”conditions between some of the nodes of the network.

Through the process called binding, which relates to the process ofplacing two or more nodes into the same network, the wireless network104 may automatically correct settings mismatches between instruments,such as the timing of the network interval and the frequency hoppingsequence. In this way, any errors made in network setting that a user,for example entered by an industrial hygienist, or administrator can becorrected automatically when two instruments bind.

The wireless network may implement a radio incorporating mesh networkingtechnology. The radio uses relatively common IEEE 802.15.4 radiossimilar to those used in ZigBee. The radio adds a network operatingsystem layer that implements a self-forming mesh routing layer.Networking functions are distributed with the network, it requires nocentral coordinator node for operation. All nodes can forward packets,creating and updating their own routing tables.

In embodiments, the end application, such as a gas detection instrument110 or 108, interacts with the networking layer using a novel approach.The radio module implements a virtual machine, with access to nearly allradio module and networking functions. The behavior of the radio andnetwork can be tailored and highly optimized by the application layer tooperate the mesh network 104 of the present invention to the specificneeds of the application using custom scripts. The wireless networkbehaviors can be highly tailored to the unique needs of gas detection.

In embodiments, the wireless network may be implemented in scripting(“radio scripts”, or “script” herein). Wireless network scripts runwithin the network operating system (also referred to as “radiofirmware” or “firmware”).

The network operating system platform also includes a hardwareabstraction layer (HAL) that insulates the application from radiohardware specifics. This allows the same script to run on differentsupported radio hardware without modification.

The radio modules use radios compliant with IEEE 802.15.4. These radioscan be operated at different frequencies. The wireless network uses the2.4 GHz band due to its nearly universal world-wide acceptance (withoutthe need for end-user licenses) and improved performance in industrialenvironments with lots of metal obstructions. In embodiments, there maybe 16 available channels, each 2 MHz wide, in a 2.4 GHz 802.15.4 system.

Referring to FIG. 4, the channels may overlap with the same spectrumused by Wi-Fi, Bluetooth, and other consumer and industrial systems, sothe wireless network may be designed to coexist with other wirelesssystems through the diversity schemes introduced herein, particularlyfrequency diversity.

With respect to power conservation, sleep cycling is a process where theentire mesh network communicates with one another during a regular, butsmall window of time. It is important to understand that the entirenetwork wakes and sleeps at the same time. The advantage of sleepcycling is reduced power consumption. By allowing nodes to sleep whilethey are off the air, the average current consumption is reduced. Theratio of communication time to sleep time may be directly proportionalto average current consumption. If radios only spend 10% of their timein the communication period, their average current consumption will beroughly 10% of their on-state current (sleep current is negligible). Theadvantage of sleep cycling in a mesh network is its simplicity—when itis time to talk, the mesh network behaves as if it were always on. Thereis no need to plan time slots for each pair of nodes or understand thephysical topology of the network, which would be easier to do with adedicated coordinator. The challenge in sleep cycled networks is keepingeveryone on the same schedule, but can be overcome with synchronizationtechniques as described herein.

Both the instrument itself (for example, a gas detector) and thewireless network radio may employ sleep cycling. Most instruments wakeonce a second (or two seconds in some cases) to measure an environmentalparameter, such as gas, and perform housekeeping functions before goingback to sleep to reduce average power consumption. As discussed herein,the wireless network sleeps too, under the direction of the networkleader. In embodiments, these two sleep cycles cannot be synchronized.Different instruments have different wake/sleep schedules, and the ratesat which gas concentrations are measured are subject to considerableregulation. A system where gas measurement rates are not deterministicwould be difficult to certify. Communicating between these two sleepingsystems is difficult.

To address the challenge of the radio and the instrument operating ondifferent wake and sleep cycles, nodes of the mesh network 104 mayemploy a shared memory interface between the radio and instrument.Described functionally, the shared memory interface may be analogous toa mailbox. Anyone can stop at the mailbox and insert items for someoneelse, while at the same time checking to see if any in-bound mail hasarrived. A second person can do the same. The two people don't need tobe at the mailbox at the same time to exchange information. If there issomething urgent in the mailbox for the other person, the indicator flagmay be raised to ensure they pick it up at the next opportunity. If twopeople arrive at the same time and try to check/deliver mailsimultaneously, they could end up dropping some mail on the ground inthe confusion. The shared memory interface uses “Request” and “Grant”lines, one each for the radio and instrument to ensure two people don'treach into “the mailbox” at the same time. The arbiter is a specialcircuit that prevents two “Grants” from being active at any moment intime. The shared memory also implements an “Urgent” line that is theequivalent of the indicator flag on the mailbox.

Referring to FIG. 5, the shared memory is described structurally. Theshared memory is a simple 32 kB static RAM chip 502. Within this memoryspace, the wireless network implements different storage locations fordifferent types of information. Commonly sent messages have dedicatedmemory locations (Static Messages 504). An example of a static messagewould be a message indicating the type of instrument attached to thenode. The radio's 520 configuration and status may be communicated usinga bank of registers 508. Incoming 510 and outgoing 512 mailboxes handleall messaging not covered by a Static Message type. Finally, some memoryis allocated to the radio module, a radio internal buffer 514, for itsinternal use, because the memory structure available within the networkOS may be limited.

Furthermore, every node (for example, portable environmental sensingdevices 108 and area monitors 110 in the mesh network 104) include aprecision timer integrated circuit 522, as described below.

In embodiments, the host instrument 518 may control nearly everythingabout the wireless network radio. Configuration messages may be providedto modify the vast majority of the radio settings. In a couple of cases,the instrument 518 may modify settings through registers as well. Theinstrument 518 may also control the state of the wireless network radio520 and can place the radio 520 into Sleep or Off Air modes at will.

In embodiments, instruments compatible with the mesh network 104 maysend a surprisingly small variety of messages. The most common messageis instUpdt( ). The payload of this message is a snapshot of theinstrument status.

In order to minimize network traffic, the wireless network may implementtwo different flavors of instUpdt( ) message. If all is normal with theinstrument, and all sensor readings are near “zero”, a short (“terse”)version of the instUpdt( ) message is sent. The terse versionessentially says “I'm Ok”. If the instrument is detecting gas orexperiencing any alarm, the more detailed “verbose” format is sent,which includes all sensor readings and alarm details.

In embodiments, a verbose message with 6 sensors may be around 40 bytes.The terse form of the message may only be 10 bytes long. An instrumentmay send status messages in the terse format unless: another instrumentrequests it to go verbose (for example if it wants to display real-timegas readings for a confined space entry), a gas reading is above thewireless deadband (currently set at 25% of the low alarm level), or theinstrument is in alarm for any reason (including panic and man-down).

When one instrument wants to see all information from another instrument(for example, when an attendant wants to display real time readings froma confined space entrant), even near-zero readings, it can request theinstrument send the verbose format by issuing the setVerbose( ) message.For example, an instrument may be requested to go into a verbose modewhen the instrument is being shadowed, such as when the instrumentwearer enters a confined space. The payload of this message may includethe number of seconds for which the sender is requesting verbosemessages be sent.

A set of messages termed “identify” may provide the relatively staticinformation needed to correctly interpret the payload of the instUpdt( )message. These messages may contain configuration details about theinstrument, including numbers and types of sensors, instrument type,serial number, current user and current site. When an instrument firstjoins a network, it may broadcast this information for other instrumentsalready in the network to save. Instruments that join later, or for anyreason need to fill in their details about another instrument canrequest an instrument resend this data (broadcast or unicast) using theidReq( ) message.

Using the information found in instUpdt( ) and the identify messages, arelatively complete picture may be generated to reflect the currentstatus of any instrument in the network.

Referring to FIG. 6A, as instUpdt( ) messages arrive, receivinginstruments are expected to extract the relevant information, correlateit to the correct instrument, and update their internal peer status listaccordingly. When a message arrives from a new instrument, as indicatedby a new media access control (“MAC”) address, the instrument is addedto the peer list and missing information is filled in from the identifymessages. A MAC address is a unique identifier assigned to networkinterfaces for communications at the data link layer of a networksegment that uniquely identifies the device on the network. When aninstrument leaves the network (e.g., user selects “disconnect”, orpowers down the instrument), it sends a special “disconnecting” message,which may be send repeatedly, and should be removed from the peer listof other nodes on the network. Instruments expect to hear an instUpdt( )message from each peer in each network cycle. If these messages stopafter the expiration of a predetermined number of network cycles, thepeer instrument may be marked “lost” and a warning may be sounded (ifenabled).

Referring to FIG. 6B, shadow gas is a term used to describe theinstrument feature where one instrument can display the real-timereadings of another instrument remotely, which may be particularlyhelpful for confined space use cases. Shadow gas feature is activated byselecting a peer instrument from the List of Instruments, as shown inFIG. 6A. A screen representing the remote instrument may be displayedand update in near real-time. In this case, even near zero gas readingsmay need to be displayed, to provide confidence to the user that thereadings are indeed being relayed to the observer. In addition to theshadow gas readings, the other instrument's location may be displayed,such as on a map.

To enable this functionality, some combination of the identify messagesand setVerbose( ) are used. When a remote instrument is selected, theinstrument will gather information such as the username, sensor details,and the like to populate the Shadow Gas display. The remote instrumentwill be set to transmit verbose readings.

One of the ways to improve robustness of a wireless network is to enlistthe help of the end user such as by displaying a relevant signal qualityindicator on the user's screen, analogous to the “4 bars” displayed onmost cellular phones. The signal quality indicator helps users diagnoseconnection issues themselves, reducing support calls. It also warnsusers of an impending loss of communication, so they can address it.Preferably, the signal quality indicator displays an indicator of thequality of connections of all of the nodes on the network.Alternatively, the signal quality indicator displays the quality of theconnection between the instrument and a predefined node on the network.Alternatively, the signal quality indicator displays the quality of aconnection between the instrument and the strongest direct connectionwith another node.

For the mesh network 104, the signal quality indicator may be derivedfrom a combination of the received signal strength (RSS) and packetreceive ratio (PRR, or “Health Counter”) of all the instruments in agiven network. This is unlike a cellular phone, which displays only thesignal quality between a phone and the nearest tower.

The RSS is available from the MAC layer of the radio for each receivedpacket. The instrument records the RSS from the last message receivedfrom each peer instrument. The signal strengths represent the lastnetwork hop taken by the message and do not necessarily reflect theweakest link in the path taken. The PRR or health counter is a measureof the recent number of received messages versus the number of expectedmessages (based on the network interval). The PRR or health counter istracked for each peer. The PRR or health counter is a counter thatbegins at a predetermined number, such as 10, and is incremented anddecremented when expected packets are received or not received,respectively. The increment and decrement values may not be the same,such as incrementing by 3 and decrementing by 2. When the health counterreaches zero, the node presumes that it is lost from the network.

The signal quality indicator is based on the product of RSS*PRR for eachnode, summed and divided by the number of instruments in the network.Alerts may be set for one or more remote nodes to monitor signalstrength, and a warning may occur when the strength drops below athreshold and an alarm may issue when signal drops out. A critical alertmay be set when the signal being monitored is a safety monitoring point.

The wireless network feature set may be implemented in several parts andlayers of an instrument, including the instrument firmware, radioscripts, and radio firmware. As features evolve, each part of the systemmay need to be updated. A robust system may be needed to allow for fieldupdates while ensuring all the pieces remain compatible.

Referring to FIG. 7, wireless network scripts may be written in ascripting language developed using the portal IDE 703. The script 702(Script.py) can then be “compiled” to bytecode for a specific radiomodule (or “platform”) into a .spy file 704 (e.g., SM200 radio moduleand an SM220 radio module have different .spy files). The Portal IDEalso provides a checksum for the compiled script (used later). Aconverter application 708, such as the Windows-based PC applicationSpyConverter may be used to convert the .spy file type 704 into a .binfile 710. The .bin file 710 is converted to a .hex file using theprogramming utility (e.g., JFLASH) and merged with other parts of theinstrument firmware. The script's checksum (from the Portal IDE), RadioHardware Version (e.g., SM200=0x01 . . . ), and the script version (3bytes—Major.Minor.Build) may be appended to the script file, again usingthe programming utility, for use by the instrument in checking theradio's programming. The checksum and version (including hardware andscript) should match what is reported by the radio module, or an errormay be generated. The complete .hex file may be loaded into instrumentmemory by the instrument bootloader, like any other part of instrumentfirmware. Accessory Software, iNet, servers, worker safety system, andthe docking stations have no knowledge that the instrument firmwareimage actually also contains firmware for the radio.

At power up, the instrument may check the radio module's script version,which may be displayed on the startup screen and available throughModbus. When the instrument detects an out of date script, it may beginthe script update process. This process uses a special communicationsport between the radio and instrument. The instrument uses an embeddedScript Uploader utility (similar to a bootloader) to transfer the file(in blocks) from instrument memory to radio memory. When complete, thenew script is checked for validity before the radio module is rebootedand normal operation commences.

Once the wireless network script is running, the instrument may alsocheck the radio module's firmware version that comes preloaded on theradio module. It is displayed on the startup screen, and availablethrough Modbus. The instrument checks to see that the radio modulefirmware version is same or newer than the revision the instrumentfirmware and script are expecting (this value is hard coded ininstrument firmware). This approach is based on the understanding that,in embodiments, features may be added, but not removed, from the radionetwork operating system. If the radio module version is out of date(not supported), the instrument may disable wireless networkfunctionality (instrument continues to operate) and instruct the user toget the radio module firmware updated.

Once the wireless network script is running, the Radio module type (orPlatform, e.g., SM200, etc.) may be read by the Radio module, translatedinto a single-byte value (e.g., SM200=0x01 . . . ) and posted to thehost interface as the Radio Hardware Version. The instrument may postthis value to modbus. At power up, the instrument may compare the RadioHardware Version to the value appended to the programmer hex file. Thismay allow the instrument to confirm any future instrument firmware orradio script updates are compatible with the radio hardware installed.

Instruments compatible with the mesh network include any describedherein as well as a barometer, which may be operable in an indoorlocation. The readings may be available using the host interface. Thebarometer reading may be saved to a Modbus register to enable factorytesting. Using the barometer the altitude of the instrument can bedetected. This feature can be used, for example, to determine the floorlevel of the instrument, such as in an underground facility. Acompensation barometer, implemented as an instrument on the networklocated at, for example, ground level can be used to determineatmospheric pressure at the reference level. Using the detectedatmospheric pressure and the reference atmospheric pressure, the floorlevel of the instrument can be determined. This information may berelayed through the network, and possibly through a gateway and to anexternal network, where the location of instruments can be displayed ona computer to show the location of instruments in latitude, longitudeand elevation.

While the wireless network is operating normally, it is sleep-cycling,frequency-hopping, and encrypted. In this mode, it may be difficult toperform certain activities like testing the radio in manufacturing orperforming an over the air update of radio module firmware. For thisreason, a Test Mode may be implemented. In test mode, the radio stopssleeping and frequency hopping, and switches the encryption key to onethat can be shared with service centers, manufacturing applications,etc. In test mode, the radio may respond to several external wirelesscommands that allow factory testing of the radio and over-the-airupdates to radio firmware. Test mode may be accessible, in embodiments,by writing a special password to the test mode Modbus register (usingsoftware like DUSS, or a manufacturing application).

In embodiments, every node (for example, portable environmental sensingdevices 108 and area monitors 110) in the mesh network 104 may include aprecision timer integrated circuit 522. This timer 522 should be astable timer, for example, stable to within a few milliseconds over anhour or more.

In most networks, synchronization is handled by a dedicated coordinatornode. In the mesh network 104, this job is performed by one of themembers of the network, called the leader. The most important job of theleader is to synchronize the mesh. The leader regularly broadcasts awireless synchronization message to members of the network that marksthe beginning of the period that the network is able to activelycommunicate, otherwise known as a “sync message” or sync( ) message.Follower nodes maintain synchronization with the leader's instructions.The leader node becomes the “master timekeeper” and all other nodesadjust their internal timers' interval and phase to match the leader'stimer.

These synchronization messages issued by the leader may also contain avalue that represents the number of nodes the leader believes arecurrently in the network. The leader bases this value on the number ofinstruments that are reporting messages, such as status messages orreadings messages, such as gas status readings. The amount of time thenetwork remains awake is preferably dependent on the size of the networkto save power. Each node calculates its awake time, based on the valuein the last synchronization message it received. For example, a networkwith only 3 instruments will spend much less time awake than a networkwith 20 instruments, saving power.

In embodiments, if a follower node doesn't receive a sync( ) message, itmay still wake up at the prescribed time and exchange messages withother nodes. Because the hardware timers are so stable, even if severalsynchronization messages are missed or corrupt, the nodes continue towake at the right time. Followers are not dependent on the leader forsecond-to-second transmissions, however, if synchronization messagesstop altogether, a follower may eventually decide that it has lost theleader and will begin the process of rejoining the network, as describedherein. Each time the network wakes, it uses the next channel in thefrequency hopping sequence, as described herein with respect tofrequency diversity.

In summary, by synchronizing the clocks of the mesh, the wirelessnetwork is capable of sleep cycling and frequency hopping, even withouta dedicated coordinator.

Because the mesh network 104 is sleep-cycling and frequency hopping, itis only operating on a given channel about once every 14 seconds andthere is little certainty regarding what set of channels a givenwireless network is using. As a result, it may be difficult to join anew instrument into an existing network without considerable delay.

The mesh network 104 solves this problem by using advertising messageson the public channels. Members of a network allow others to join (orre-join) a network by “advertising” on pre-defined public channels. New(or lost) nodes can locate an existing network by listening on thesechannels. During every network cycle, the leader and all followersadvertise the current network parameters on both public channels using amessage, an example of which is called boPeep( ). The boPeep( ) messagemay include all information needed to synchronize with an existingnetwork, including synchronization of timers, the number of devices onthe network and the identity of the frequency hopping sequence. Newmembers or members that have lost synchronization with the network mayuse these network parameters to join the network and re-synchronize withthe leader. boPeep( ) messages (unlike most other wireless networkmessages) may be sent only with a single network hop. This is done toprevent flooding the network with retransmissions. Further, followersmay only send boPeep( ) messages in network intervals when they havereceived a sync( ) message from their leader. Therefore, each followerhelps identify only the current network leader.

Referring now to FIG. 8, most routine wireless messages are broadcastwithout collision avoidance or collision detection measures enabled,which is a byproduct of the mesh network's 104 synchronization scheme.During a first time interval (T0 to T1), followers listen for the leaderto broadcast a sync( ) message. When the sync( ) is received, thefollowers calculate a time for the next expected network interval. If async( ) message is not received and has not been received for apredetermined number of network intervals, the node determines that ithas lost the network and begins a network rejoin sequence, as describedbelow.

In embodiments, to compensate for the negative aspects of lack ofcollision avoidance or detection, the awake time during the networkinterval is divided into sections (S0, S1, S2, . . . , Sm) during whichnodes choose a turn to broadcast to help spread out the network trafficover the time the network is active (thus reducing the probability ofcollisions). Messages of the highest priority, such as instrument statusmessages, are sent first during period T1 to T2. All other messages aresent after each instrument has been given an opportunity to send itsstatus message (T2 to T4). Transmissions will stop, and then a suitabletime is left to allow all messages to propagate the network (T4 to T5).Finally, if a sync( ) message was heard in that network cycle, nodes goto each public channel and send a boPeep( ) message to advertise thenetwork's parameters for lost nodes or new nodes wanting to join (T5 toT6). After T6, the node goes to sleep until the next network interval.

In embodiments, the number of slots (S0-Sm) may be proportional to thenumber of instruments in the network (n), and when number of slots isproportional to the number of instruments in the network, the leaderbroadcasts (n) in each sync( ) message. Each node calculates the networktiming and selects a slot for broadcast at random. While this does notguarantee a dedicated slot, this mechanism may still be effective atspreading network traffic. Consider also that each node's clock may beslightly out of phase with the other nodes—the clock synchronizationallows nodes to be as much as 10 mS out of phase with the leader. Atypical wireless transmission may take less than 4 mS. Another key pointis that each node's slot for broadcasting is randomly reselected on eachnetwork interval. Even if a node happens to transmit at the same time asanother node, those two nodes are highly unlikely to select the sameslots in the next network interval. Even with large networks, mostmessages get through and any one node is unlikely to be blocked forseveral back-to-back messages. Further, by increasing the number ofslots available for transmission versus the number of devices in thenetwork, the chance for collision is reduced.

In embodiments and referring to FIG. 8A, the wireless network chooses a“leader” from the members of a network. Any node must be prepared to dothe job of the leader. In the event that the current leader suddenlydisappears, a different node performs the job of the leader. The processof picking a leader consists of nominations, elections, and ongoingmonitoring.

In embodiments, in a first step 800, when a new node goes to the publicchannel to search for a network, it listens (such as for 4 seconds) fora boPeep( ) message on a first public channel, which indicates there isalready an active leader. In a step 802, if a boPeep( ) is heard, thenode assumes the role of a follower of the node from which the boPeep( )was received. In a step 804, if no boPeep( ) is heard, the new nodeswitches to the secondary public channel and listens again (such as for4 more seconds). If a boPeep( ) is heard, the node assumes the role of afollower of the node from which a boPeep( ) was received in the step804. If no boPeep( ) is heard on either public channel, the node returnsto the primary public channel and begins the election process in a step806.

In embodiments, in the step 806, the node sends a nominate( ) message,which may include a leader qualification score. The leader qualificationscore may be calculated based upon instrument type, battery state ofcharge, and past signal quality. Instrument type may be a relativemeasure of suitability as a leader—e.g., a fixed area monitor makes abetter leader than a portable instrument. These parameters determinewhich radio will eventually be selected for the leader role. As furtherexample, instrument types with large battery capacity make the bestleaders because leaders consume more power than followers and a largebattery leads to less leader interruption. Some instrument types may belarger and have greater range due to power and antenna size. Someinstruments, for example fixed area monitors, make good leaders becausethey do not move, may have higher power and are typically located nearthe center of the mesh.

In embodiments, in a step 808, the nominating node may listen for aperiod of time on a public channel, such as for 1 second. Any other nodelistening may compare the nomination message and send a concede( ) ornominate( ) message depending on how the node's own leader qualificationscore compares to the nominating node's leader qualification score.Next, one of the following cases occurs: 1) in a step 810, if thenominating node hears concede( ) messages, but no nominate( ) messages,it declares itself leader by issuing a boPeep( ) or 2) if the nominatingnode hears any nominate( ) message, it compares the sender(s) leaderqualification score to its own and in a step 812, if the sender's scoreis better, it sends a concede( ) message, or 3) in a step 814, if thesender's score is worse, it sends another nominate( ) message and waitsan additional period of time, such as for 1 more second. If thequalification scores are the same, the lower MAC address is consideredbetter. In a step 816, if the nominating node hears no messages after 1second, it sends another nominate( ) message in step 806, which may besent repeatedly, such as up to 4 more times if the nominating node hearsno message. If, after 5 seconds or a predetermined number of nominate( )messages, for example, the nominating node has heard no messages, itgoes back to listen on the public channels in step 800 for an additionalperiod of time, such as 8 more seconds, before repeating the electionprocess.

After being selected as the leader of a network, the leader will beginto frequency hop by changing the broadcast channel in each successivenetwork interval. By broadcasting the boPeep( ) in the public channel,it will allow the nodes that lost the election to join its network andfollow its frequency hop sequence.

In embodiments, certain area monitors on the wireless network maycontinue this process indefinitely, so that whenever a second areamonitor is powered on (and on the same channel), they will connectautomatically. Certain portable gas detectors may be expected to stay inthis searching mode only for a limited time (e.g., minutes), before theradio is powered off to save power.

In addition to synchronizing the network, the leader has a couple ofother important jobs. One may be a process that prevents multipleleaders of a given network. This step is important in resolving caseswhere the leader becomes separated from the network, or one half of anetwork becomes separated from the other, such as when the leader movesaway from multiple devices. In such a circumstance, the devicesseparated from the leader will nominate a new leader. However, if thetwo leaders come into proximity with devices that had previous followeda different leader, confusion can result from the existence of twonetwork leaders with the same network ID. These cases can result inmultiple leaders of the same network, which in turn can lead to erraticbehavior. Therefore, it is necessary for leaders to occasionally stop tolisten for other leaders in the network.

In that regard and referring now to FIG. 9 and FIG. 10, at a regularinterval (such as every 60 seconds), just after the network wake periodends, instead of going to sleep the leader remains awake (step 902) andgoes to the public channels and listens for advertising messages todetermine whether other nodes are leaders of other networks that are inrange (step 904). During this time, the leader intentionally skipssending a sync( ) message for the next network cycle. This causes theleader's own followers not to send boPeep( ) messages in that cycle.During this time, the leader listens for any boPeep( ) messages on thepublic channels. If the leader hears one, it means that there is anotherleader within range operating under the same network name. The leaderrelinquishes leadership and begins to follow the other leader (step906). The leader's old followers (through leader health monitoring) willrealize their leader is gone, and will also go to listen on the publicchannels and will find a new network. To maintain the leader healthmonitoring, a leader health counter is maintained and incremented by onewhen the leader is heard in a network interval and decremented by one ina network interval where the leader is not heard. When the leader healthcounter reaches zero, the node presumes that it has lost its leader andbegins the process of finding a new leader. Therefore, this handles thedifficult case where a network is split in two. Each half elects its ownleader but is still operating under the old network name. When these twogroups come back into range of one another, the behavior described abovecauses them to be rejoined. The new leader also sets a new awake timeinterval for the network by including the network size n=# peers+1 inthe payload of the sync( ) message. The leader's radio bases the networksize on the number of peer instruments reported by its instrumentsoftware (active or lost) plus 1 (the leader). The network size(peers+1) is also sent in each boPeep( ) to prevent more than theallowed number of instruments from joining one network.

If a new leader is not elected (step 908), the leader continues in itsrole as leader and resumes sending sync( ) messages at the beginning ofnetwork intervals.

The leader also needs to be aware of a special situation called “Leaderof none.” Considering the case where all peers have left a network (noactive or lost peers), the leader should not continue to operate thenetwork without followers. Instead, the instrument will relinquishleadership and will return to listening on the public channels, ready toform a new network when another instrument is detected.

In embodiments, the wireless network may use frequency hopping, whereevery network interval occurs on a different channel, or frequency. Anexemplary process and architecture for frequency hopping is describedherein. In an embodiment, the channels (16 channels in the case of anIEEE 802.15.4 network) may be divided between active channels and publicchannels. Preferably there are two public channels and the remainder ofavailable channels are active channels. The active channels may be usedin the hopping sequence, whereas the public channels are used forforming/joining/rejoining networks, as described above. Preferably,public channels will be non-adjacent and should utilize frequencies thatare not heavily utilized (e.g., between WiFi bands, managed spectrum,etc.)

Active channels may be, by default, all channels other than the publicchannels; however, channels can be “blacklisted” by using an activechannel mask. Some active channels may be blacklisted due to localregulations or due to high traffic levels known to be on the channel.For example, a wireless video camera operating on a channel will createheavy traffic on that channel, and therefore it may be desirable toavoid that channel.

During operation, a different active channel may be used for eachnetwork cycle, called frequency hopping. The order of the hopping may bea repeating nonrandom sequence or a pseudorandom sequence, such as onecalculated using a linear congruential generator (LCG).

The inputs to the generator (“hopping parameters”) are a multiplier,intercept and a seed. At power up, each node randomly chooses a validset of hopping parameters and saves them, in case it is ever called onto lead a network. In an embodiment, using the recommended settings withpublic channels 4 and 9 in a 16 channel environment, and no channelsblacklisted, the algorithm generates hopping sequences where the nextchannel is always at least 2 channels away from the current channel(non-adjacent). If either the public channels or masks are modified,this may not always be the case.

When a node wins a leader election, it sends its hopping parameters inthe advertising message (boPeep). Followers compute the sequence, usingthe leader's parameters, and advance to the next channel, waiting tohear the leader's sync( ) message. With each network interval, theleader and all followers advance one step in the sequence.

Leaders and followers transmit the hopping parameters on both publicchannels in the advertising message (boPeep) near the end of everynetwork cycle, to allow other instruments to find the network. Aninstrument wanting to join a given network, need only listen on one ofthe public channels to compute the proper sequence and next channel. Thenode advances to the next channel and waits for the leader's sync( )message to begin hopping.

The LCG calculates the next channel using the formula:X _(n+1)=(aX _(n) +c)mod m

where X is the sequence of pseudorandom values, and

m, m>0 the “modulus”

a, m>a>0 the “multiplier”

c, m>c≥0 the “intercept”

X₀, m>X₀≥0 the “seed”

These values are all integers that define the sequence. In a sequencewhere the modulus is known, for example a network with 16 totalchannels, the modulus may be assumed by all of the nodes rather thantransmitted in a sync( ) message. Further, when a public channel or abacklisted channel is the result of the sequence the node can eitherchoose the next non-reserved channel or the next channel in thesequence.

Using wireless technology introduces certain information security risks.The system may include measures that prevent unauthorized listening-into instrument readings and status, prevent injection of false/misleadinginformation into a network (like false alarms), and prevent jamming orother denial of service attacks that would prevent effective use of thewireless feature set.

Wireless message contents may be encrypted by default. Encryption meansthat the contents of a wireless message are garbled and unrecognizableunless a receiver knows the secret password, called a “key.” Thewireless network may use Advanced Encryption Standard (AES) encryptionwith a 128 bit key length for messages sent wirelessly. This encryptionis standard for the 802.15.4 radios used. These radios may have built-inhardware encryption engines, so using encryption has minimal impact onthroughput or power consumption.

Multiple approaches to wireless network security may be possible. In oneapproach, each wireless network-compatible device may leave the factorywith a default key. The key is kept private, and it is not visible tothe end user in any device or software—it is embedded (and, inembodiments, hidden) within the instrument source code. Since allinstruments have the same default key, there is no need to transmit itbetween devices, just a need to agree to use the default key. In anotherapproach, if the user wishes, they can enter a customer key into theirdevices, using the instrument UI, iNet, or other maintenance tool—again,once entered, this key is never displayed. To ensure that newinstruments can be added to a network using a custom key, the key may beshared as part of the binding process.

The wireless network's system of binding also helps protect fromunauthorized access to a given network. To participate in a givennetwork, a user first learns the network's unique name through closecontact with an instrument that is already a member of the group (via IRor Near-Field Communications).

Binding is the process of joining two or more wireless devices into thesame wireless network. Implied within binding is the understanding thatthe devices want to share alarms and/or information—that is, there is nonetwork without intent to share information. The binding process of thepresent disclosure does not include the concept of being connected forfuture use. If a node is connected to the network, it is sharing andbroadcasting. No further authentication is needed if the devices arebound to the network using the touch process, described further below.Anyone in the network is trusted with allowing a new entry. Binding issimilar to the process of “pairing” used in point-to-point networks,including Bluetooth. However, the network 104 is a mesh network, so moreoften than not, binding is actually bringing a new device into anexisting network including several other devices, so “pairing” is notentirely accurate because it implies only two devices are involved. Thatsaid, any reference to “pair” or “pairing” herein can encompass thebinding described herein. In certain embodiments, the mesh network 104may be established in instruments 110 and/or 108 and/or gateways by anNFC binding process where the network parameters are passed and peernetworks in area monitors may be established by choosing the same namednetwork.

The wireless network may have multiple binding methods, such as NamedNetwork and Secure Simple Binding.

Named Network is implemented in the wireless network as a list ofpredefined networks, say “A” through “J”, which will be called“Channels” in this example, though they may have nothing to do with thefrequencies used. Each wireless network-compatible device may comepre-programmed for these Channels when they leave the factory.Connecting two devices may be as simple as making sure they are both setto the same Channel (letter). Two instruments set to the same Channelmay connect automatically at power up if they are within range of oneanother.

With Named Networks, the selected channel is defaulted at the factory,and remembered through power cycles. At power up, a device may seek outand connect to any other devices in range and set to the same channel.Because their primary wireless network use case is replacement of daisychain cables, area monitors may use Named Network as their primarybinding mechanism. Area monitors may ship with a default network settingand connect “out of the box”. More sophisticated users can set updifferent groups of area monitors by using different channels fordifferent groups.

Area monitors may remember their network settings and try to reconnectevery time they are powered up. This means that area monitors couldconnect unintentionally with an existing network. This problem should bemanageable, given the smaller number of these devices and thegenerally-higher level of user expertise, instruction, and training.

Secured Simple Binding (SSB) may be implemented in the wireless networkby passing network “secrets” (like the PIN in Bluetooth). SSB takesadvantage of a second, simple, short-range communications technology,called an Out-Of-Band (OOB) link, to pass a network's credentials to ajoining member. In the case of the wireless network, an instrument'sinfrared may be used (e.g. IrDA) and Near Field Communications (NFC) forthe OOB link.

Portable instruments with the wireless network compatibility may useSimple Secure Binding (SSB) as their primary mechanism. Near FieldCommunication (NFC) may be used for the out-of-band (OOB) link. Theportable binding implementation may be biased towards 1) preventingunintended connections and nuisance alarms, and 2) ease of connection.In embodiments, portables may forget their network associations at powerdown. When the instruments power up, they are in a disconnected statebut are always watching the NFC interface for another instrument. Whentwo portables are placed together, they connect to the same network,with no other user intervention required. The simple action of touchingthe instruments together ensures the connection is deliberate.

There are three scenarios to consider: 1. If neither device is currentlyin a network, the two devices may form a new network and connect.; 2. Ifone device is already participating in a network, it passes the existingnetwork credentials to the new instrument and allows it to join theexisting network.; and 3. If, on the other hand, both devices arealready part of different networks, the binding process fails and bothinstruments display a screen asking the user if they want to leave theirold network. After at least one of the users leaves their existingnetwork, the binding process can be repeated with success.

Area monitors may also implement Simple Secure Binding (SSB) as asecondary mechanism. This is a robust method for connecting any two areamonitors. Regardless of how their configurations have been changed(custom encryption, different channel settings, etc.), performing SSBwill arbitrate these settings so they connect. In the same way, a rentalor replacement monitor can be added to the network without the need foran expert user, specialized software (e.g. ISAS software or iNET), andthe like. SSB on the area monitor may also be used to connect a portableinstrument to join into an existing area monitor network.

The following information may be communicated during the Secure SimpleBinding process: Low 3-bytes of the MAC Address, Proposed Network Name,Active Channels to be Used, Primary Public Channel, Secondary PublicChannel, and Custom Encryption Key (if used).

Once this information is exchanged, the instruments may have all theinformation they need to complete a connection. A confirmation tone(and/or vibratory signal) may be emitted to indicate that theinstruments no longer need to be held together.

After two instruments exchange the binding information, they must decidewhich instrument's settings will be used in the network. If oneinstrument is already part of a network (i.e., it sent an “Allow”message), its settings are used. If neither instrument is part of anetwork, the settings of the instrument with the lower MAC address areused, except in the case where one instrument has custom encryptionenabled and the other has default encryption enabled. In this case,custom encryption is considered more robust and will be used.

After arbitration, the instruments apply the appropriate settings to theradio module and attempt to connect. When the connection is successful(indicated by receipt of at least one other instrument's statusmessage), a confirmation tone may sound and the wireless icon may beilluminated. The connection process is expected to complete within a fewseconds.

With respect to performance, range is a function of link budget minuspath loss. Link budget is the difference between transmitter outputpower (including antenna gain/loss) and receiver sensitivity. Outputpower is limited by regulations and/or battery life, while receivesensitivity is a function of electronics design quality and data rate.

Shown below is the free-space path loss equation that predicts range (d)of a RF signal.

$d = {\frac{\lambda}{4\pi}\sqrt{\frac{P_{t}G_{t}G_{r}}{P_{r}}}}$

-   -   P_(t) is the transmitted power, P_(r) is the received power    -   G_(t) is the transmitter, G_(r) the receiver antenna gain    -   d is the distance between transmitter and receiver, or the range    -   Lambda is the wavelength

$\lambda = {\frac{c}{f} = \frac{{Speed}\mspace{14mu}{of}\mspace{14mu}{light}}{Frequency}}$Eqn. 1

Using a radio module as example: P_(t)=3 dbm; P_(r)=−100 dbm; and d=250m, including a conservative fade margin of 15 db. Fade margin capturesthe practical sensitivity of the receiver, and includes antennapolarization, reflections, multi-path interference, etc. A fade marginof 6 dB would represent ideal conditions (clear weather, antennasaligned, etc.); a more conservative number might be 15 dB.

Practical range in an industrial setting is different from a free-spaceenvironment. Through a typical warehouse environment, actual range forthe radio modules may be about 75 m. Line of site through a largefactory may be approximately 100 m. Actual range may vary widelydepending on the environment, and the mesh topology extends theeffective range dramatically. Height off the ground may also impactrange.

In embodiments, the mesh network 104 may be designed to operate withbetween 2 and 25 instruments in a given network. If there are too fewnodes for an environment, the network may not have enough paths to beeffective. When networks grow too large, the individual nodes have tocompete for the shared resource of network bandwidth. Therefore, inembodiments, the optimum network size is typically between 8 and 15instruments.

Because of the frequency hopping and the short transmission time of802.15.4 radios, hundreds of instruments can operate within the samearea without interference, provided they are operating on differentnetworks, as described herein. The discussion herein with respect tojoining/re-joining a network provides details on how network size iscontrolled.

Hardware enabling wireless network-compatibility may include: An802.15.4 Radio system on a chip (“SoC”), supported by a networkoperating system (typically a pre-certified module); memory IC andcircuitry that implements a shared memory interface; and a precisiontimer used to maintain network synchronization. In some embodiments, abarometer may also be included.

Hardware enabling wireless network-compatibility may be implementeddirectly on the portable gas detecting instrument mainboard. For modelsof the portable gas detecting instrument without wireless functionality,these parts are depopulated. In other embodiments, such as for areamonitors, the hardware enabling wireless network-compatibility may beimplemented in a pluggable PCB (module), such as for area monitors. Themodule may also add a GPS receiver (which may or may not be populated).While not technically part of the feature set, the GPS feature may beimplemented as part of the script running on the Radio SoC. Although aslightly different radio module may be used on area monitors, the othercircuitry may be identical to the hardware implementation for portableinstruments (other than GPS).

FIG. 11 depicts the wireless network architecture. In FIG. 11, thestructure of two instruments 108, 110 with radio modules that interactin a wireless mesh network is depicted. Each of the instruments aredepicted as being similar, but the instruments may be differentinstruments, and their structures may be that of a portable device, areamonitor, or the like. Each instrument may have one or more endapplications, such as gas detection, peer alarms, shadow gas, and thelike. Each instrument may be involved in network management, such aswith activities such as peer instrument list, signal quality,connect/disconnect, identify, and the like. An instrument-radiointerface 1114 (e.g. serial, digital I/O) is shown operating to connectthe instrument application component with the radio module 1118 and itswireless network protocol. A wireless interface 1120, the wireless meshnetwork, is shown between the radio modules 1118. FIG. 13 depicts thewireless network fitting in a 7-layer OSI Model.

In embodiments, the same wireless radio useful in the wireless networkmay be used in a master-slave relationship between an instrument and itsaccessory. In this case, each accessory device would include a similarradio as the instrument. Possible accessories include auxiliary alarmdevices, smart sample draw pumps, or even a bridge to a smartphone orother mobile gateway or computing device. The bridge would communicatewith the instrument using the wireless network technology but convertcommunications to another format. The other format could be Bluetooth toconnect to a smartphone 118, or an industrial protocol like HART orWirelessHART, or WiFi. Accessories could also include additional sensingdevices (gas, workers vital signs, or otherwise) that would share thedisplay, datalog, and alarms already found in the gas detector. Anotherexample is an adapter that holds an inline benzene filter, andcommunicates with the instrument to indicate filter state(engaged/bypassed) or filter age.

In certain embodiments, the parts of a gas detector (sensor, display,alarm, etc.) may actually be separate devices, connected wirelessly.With this model, a sensor could communicate with a smartphone 118.

FIG. 12 depicts how the hardware enabling wireless network-compatibilitycan be extended to a platform using gateways 112 to the Internet for theend application of remote monitoring and the like. For example, thegateway device 112 may receive data from an instrument 108, 110 throughthe mesh network 104 and transmit it to the cloud via cell, Wi-Fi,Ethernet, or satellite. The gateway device 112 may be intrinsicallysafe, extended battery power (such as 7 days), rugged, andwall-mountable or transportable. FIG. 12 depicts an instrument 108, 110structure similar to the ones shown in FIG. 11, but the instrument 108,110 is in communication with a gateway 112 in this instance via awireless mesh network, such as the mesh network 104. The gateway 112 mayinclude a radio module 1118 with a serial connection to a single-boardcomputer 1214. The single-board computer 1214 may include a gatewayapplication 1218 that is in communication with a database, and with anetwork through a communications protocol, such as the internet,Ethernet, cellular, WiFi, satellite, and the like. The network mayultimately allow an end user to connect to the worker safety system witha PC/mobile device 1220. The gateway 112 is shown in FIG. 1 wherewireless network-compatibility is extended to a platform using gateways112 to the Internet. Data may be transmitted between devices using themesh network 104 and data may be transmitted to the gateway 112 usingthe mesh network 104. The gateway 112 may transmit data to the cloud viacellular technology, WiFi, and/or satellite where it may be used in avariety of applications as further described herein. For example, when agas detector goes into alarm and the data are transmitted back to thecloud, a remotely located supervisor may deploy a response team, send amessage back to the gas detector, call the worker with the gas detectoron a separate phone or on the gas detector itself if it possessestelecommunications functionality, ask another nearby worker to check inon the worker, and the like. Data may be aggregated over time regardingalarms and other safety-related data to identify risks or safety-relatedissues in an area, as is described herein.

With continuing reference to FIG. 1, data may be transferred from theinstruments 108, 110 to other devices, such as mobile devices, tabletcomputers, local computers, beacons, and the like using communicationsprotocols such as NFC, Bluetooth and the like. In an illustrativeexample such as that depicted in FIG. 1, an API 114 may be used totransfer data between the instruments 108, 110 and smart devices118/mobile gateways 131, wherein the smart devices may use the dataitself or transmit the data on to a remote server 130 or the cloud viaWiFi, cellular, satellite or the like. In some embodiments, theinstruments 108, 110 may transmit data directly to a remote location,such as by having integrated WiFi, cellular or satellite technology.There may be two-way communication through the device 118 or mobilegateway 131 such that remote computers or applications running in thecloud may be used to control, configure or otherwise communicate withthe instruments 108, 110 through the device 118 or mobile gateway 131.For example, a report from a gas detector or a group of gas detectorsthat a gas threshold has been reached may be sent to a remotely locatedsupervisor. The supervisor may be enabled to take many actions throughthe worker safety system, such as communicate back to the instrument,change the display on real-time signage, take control of a local device,such as a drone-mounted gas detector or camera, and the like. Inembodiments, the worker safety system may automatically take control oflocal devices or instruments based on a report from an instrument.

Referring now to FIG. 3, a plurality of portable environmental sensingdevices 108, 110 in a work area adapted to communicate with one anotherin a mesh network 104 are shown. In FIG. 3, some devices 108, 110 areshown in communication with a remote server 130 or computer via acommunications facility, such as a dock 122, gateway 112, mobile gateway131, or smart phone 118. Other devices in the mesh network 104 may notbe in direct communication with the remote server 130 or computer andinstead rely on receiving data or instructions through the mesh network104 from other devices 108, 110 that are in communication with remoteservers 130 and computers. The communications facility transmits datafrom at least one of the plurality of portable environmental sensingdevices to a remote computer, wherein the remote computer is configuredto monitor at least one of a hazardous condition and an activation of apanic button in the work area based on data from the at least one of theplurality of portable environmental sensing devices. The remote computeris configured to receive, from the at least one portable environmentalsensing device, an alarm related to the hazardous condition oractivation of panic button, and transmit to any of the portableenvironmental sensing devices an instruction to be propagated throughoutthe mesh network. The instruction may be a request to check the safetyof a user of the at least one portable environmental sensing device, anevacuation instruction, a risk mitigation instruction, and the like. Theremote computer may further be configured to display the location of theportable environmental sensing devices in a map of the work area andtransmit the map for display on any of the portable environmentalsensing devices. The data transmitted by the communications facility canbe sensed gas data, wherein the hazardous condition is based on thesensed gas data exceeding a threshold. The remote computer may befurther configured to display the sensed gas data in a map of the workarea, wherein a size of the representation of the gas data isproportional to the gas level. The remote computer may be furtherconfigured to request an emergency response at the location of the atleast one portable environmental sensing device.

In an illustrative example, applications resident on the smart devicemay send data to the cloud. Applications served by a cloud or otherremote server 130 may receive data sent by smart devices or from thegateway 112 and provide web interfaces for various end use applications,such as monitoring, mapping workers and alarms/events, notifications,alarms, e-permitting, compliance, emergency response, safetyinspections, accountability, risk management, compliance, lone workersolutions, worker networks, 3^(rd) party integration, device/instrumentcontrol, and the like, as will be described further herein.

Continuing with FIG. 1, the instrument 108 is depicted as incommunication with a beacon 102. The beacon 102 allows for broadcastinginformation to the instrument 108. In embodiments, the data broadcast bythe beacon 102 may be stored by the instrument 108.

FIG. 1 also depicts an NFC tag in relationship to the instrument 108 andthus other components of the system. For example, data collected by theinstrument 108 from the NFC tag may be used to tag gas detection data toenable quickly identifying the gas detection instrument operator andlocation to make the gas detection information more actionable.

Gas detection instruments, portable environmental sensing devices, andother safety devices with integral technology that collects temporaryassignment and location information may enable valuable insight into gasexposure data, safety events and user behavior, while being useful whenmanaging assets and investigating potential issues. Tagging gasdetection data and other collected data allows anyone reviewing the datato easily see who had the instrument and where the operator was usingit, making the information more actionable. This disclosure may refer togas detection instruments and area monitors in the description andexamples of the systems and methods. Such references are meant to applyto the components of the system described herein, such as environmentalsensing device 108, area monitor 110, gateway 112, API 114/Smart Device118 or mobile gateway 131, it should be understood that otherenvironmental sensing devices, area monitors, and components may be usedwith the embodiments described below.

NFC tags are short range, small, non-powered tags with a small memoryand a radio chip attached to an antenna. Having no power source, theydraw power from the device that reads them, thanks to magneticinduction. When a reader gets close enough to a tag, it energizes it andtransfers data from that tag. The assignment tag may be small, light,require no battery, and may withstand harsh outdoor environments.Assignment tags may be in multiple styles, such as a sticker tag, awaterproof sticker tag, an outdoor tag, a keychain tag, and the like.The assignment tags may be continually overwritten as needed or lockedso that they cannot be reprogrammed.

The gas detection instruments with NFC technology may support multipleassignment types, such as recurring and temporary assignments. Arecurring assignment may persist with the instrument when the instrumentis restarted. A recurring assignment may be made using an application orsoftware, such as iNet Control, DSSAC (Docking Station Software AdminConsole), or accessory software resident on the instrument or othercomponent of the system that communicates with the instrument. Atemporary assignment may be made via an application or through theinstrument settings. Temporary assignments may overwrite recurringassignments and stay with the instrument until it is restarted. Uponrestart, an instrument with a temporary assignment may revert to therecurring assignment, if one is available. If there is no recurringassignment, the instrument may be unassigned. Alternatively, to remove atemporary assignment, the assignment tag may be re-touched to theinstrument when the assignment is no longer needed.

In an embodiment, and referring to FIG. 14, in order to make use of theNFC assignment capabilities of the gas detection instrument, assignmenttags 1402 may be programmed with an assignment using an assignmentapplication 1404 or other assignment software. The tags may need to onlybe programmed once. The tags may then be distributed to instrumentoperators or installed at a location. Then, instrument users may touchthe gas detection instrument 108 to an assignment tag so that the NFCradio in the instrument may sense the assignment tag.

Assignment tags for identifying individuals may be programmed with avariety of identification data, such as name, size and weight (such asto be able to calculate a person-specific gas hazard threshold), typicalwork locations, job function, security and or authorization informationwhich may include whether the user is authorized to use a specificinstrument or be in a specific location, typical instruments used by theuser, pre-existing events caused or experienced by the user such asprior alarms or gas events, languages known by the user, prior alarms,and the like. Assignment tags for identifying locations may beprogrammed with a variety of data, such as location within a space, GPSlocation, equipment at the location, fuel sources at the location, knownhazards at the location, typical gas concentrations for the location,other environmental conditions for the location, recent gas events atthe location, recent man down alarms triggered at the location, recentalarms triggered at the location, recent messages triggered at thelocation, and the like.

Referring now to FIG. 15, as described herein the worker or industrialsafety monitoring system may include a personal NFC tag 1502 assigned toa worker, wherein the tag assigned to the worker comprises identityinformation of the worker, such as name, size, weight, jobtitle/function, company, languages spoken, certifications/licenses,accommodations, approved tasks, approved locations, approved equipment,hours worked, typical work location, a typical instrument/equipmentused, a pre-existing concern, a prior alarm, a prior gas or safetyevent, any prior radiation exposure levels, a prior message, a securityclearance, and the like.

NFC assignment tags 1502 may be carried by workers or attached to a namebadge, employee ID, hardhat, tool belt, or other personal item. Thesystem may also include and/or interact with a plurality of location NFCtags 1504 assigned to locations, each location tag placed in a locationcomprising information of the location in which the location tag isplaced. Certain parameters associated with the location may beprogrammed into the NFC tag, such as for example, location name,latitude/longitude/GPS coordinates, typical temperature, typicalhumidity, a level of authorization needed to enter/service the location,the type of equipment in the location, a certification/license needed tooperate equipment at the location, personal protection or safety gearrequired, instructions to be followed, instructions for on-siteequipment, gas detection instrument dock nearby, a fuel source at thelocation, a known hazard at the location, a typical gas concentrationfor the location, an environmental condition for the location, a recentgas event, a recent man down alarm, a recent alarm, a recent message,and the like.

A portable environmental sensing device 1508 detecting data of anenvironmental parameter may be configured to (i) read the personal NFCtag and store the identity information of the worker using the sensingdevice, (ii) read at least one of the plurality of location NFC tags andstore the information of the location of a location tag read by the atleast one portable environmental sensing device, (iii) associate thelocation information, identification information, and/or any parametersdetected by the sensing device and store such associated information,and (iv) transmit any of the information above to other components ofthe system. Note that the transmission of data may be accomplished inaccordance with the methods described herein, such as via a P2P network,mesh network and/or to and through the cloud in manners describedherein. Components receiving and operating on the data may be asdescribed herein. In accordance with the description herein at least oneprocessor 1510, which for example may be located in another instrument108/110 or part of the remote server 130, may be in communication withthe at least one portable environmental sensing device 1508 and mayreceive any of the information above (i)-(iv) from the at least oneportable environmental sensing device 1508. In embodiments, the at leastone processor 1510, itself, may be programmed to determine anenvironmental parameter of the worker using the sensing device 1508 andthe location of the determined environmental parameter based on the datait received from sensing device 1508. The system may further include aremote server 1512 comprising a memory 1514 in communication with the atleast one portable environmental sensing device 1508 that stores thedetected data and the information in a data log. The system may furtherinclude a wireless transmitter 1514 that transmits, including in themanners described herein, the detected data and the information to acloud-based or other remote server 130 or log. The transmitter may bethe gateway 112, API 114/Smart Device 118 or mobile gateway 131 asdescribed herein in connection with FIG. 1. In embodiments, the wirelesstransmitter 1514 transmits the detected data and the information toanother portable environmental sensing device 1508 or other safetydevice. For example, a detected event on a first portable environmentalsensing device may be transmitted to one or more other portableenvironmental sensing devices, gas detection instruments, safetydevices, servers, computers, smartphones, and the like in the form of amessage, an alert, or raw data, wherein the transmission may include theinformation derived from the NFC tags.

In an aspect, workers may wirelessly enter a name and a location intothe device 1508 or instrument 108/110 simply by tapping the NFCassignment tag to the instrument. Alternatively, location informationmay be automatically collected via GPS or other location sensingtechnology. Once the user and/or site information has been transferredfrom the assignment tag to the instrument, data recorded by the device1508 or instrument 108/110 may be tagged with the user and locationinformation and saved, in the instrument data log or wirelesslytransmitted to a cloud-based or other remote server 130.

In another example, each employee may receive his or her own assignmenttag identifying them which can be attached to a name badge, employee ID,or other personal item. Then, each day, the employee may pick up aninstrument from a shared pool or tool crib, wherein the instruments maybe compliant, calibrated, and/or bump-tested, at the start of his or hershift. When the instrument is touched to the assignment tag, theassignment is complete. The device may be further configured to theuser's needs and/or specification, and may also include data about theuser. This may be an example of a temporary assignment. In anotherexample of a temporary assignment, the assignment application may beused to assign the location “Tank 1” to an assignment tag. The tag canthen be installed at the entrance to Tank 1. When instrument operatorsenter Tank 1, they can touch their instruments to the tag and thelocation assignment will be saved to the instrument. These examples maydescribe separate scenarios or a single scenario. For example, theinstrument operator may temporarily assign themselves an instrument fromthe tool crib, then assign the ‘Tank 1’ location upon arrival to Tank 1.Thus, data will be tagged with both the user identification and thelocation at which other data are collected.

In embodiments, using NFC tags, a permission-based perimeter fence maybe established. For example, if only certain users are allowed to enter‘Tank 1’, only those users may be able to assign the ‘Tank 1’ locationto their instrument, which may then be used for electronic entry to‘Tank 1’, for example.

In embodiments, the system of FIG. 15 includes a beacon 102, which mayrepeatedly transmit an informational message, the beacon's payload.

In embodiments, customized on-screen messages may be provided to the gasdetection instrument with specific information or instructions, such asinstructional text to assist users in knowing how to react properly inthe event that an instrument alarm occurs. The messages may beprogrammed into the instrument itself or any system component incommunication with the instrument and automatically triggered, such asthrough detection of one or more particular gases or detection of athreshold amount of gas. In other embodiments, the messages may bemanually delivered, such as from a supervisor, another instrument user,a facility manager, an instrument manager, a control center, or thelike. Certain messages may display during the instrument start-upsequence. Certain messages may display during gas or other safetyevents. In embodiments, a unique instructional message may be set foreach of these events for each sensor: gas present (alert, low alarm, andhigh alarm), STEL (short-term exposure limit), and TWA (time-weightedaverage). For example, an alarm action message may be programmed foreach all alert/alarm set points for each sensor of the gas detectioninstrument to tell the user, in their native language, whether theyshould wear a respirator, leave the area, seek shelter or take whateveraction is dictated by the company emergency response plan. Alarm actionmessages mean that an instrument user need not be trained to interpretand understand the meaning of all gas readings, rather the user simplyneed to read the display and heed the instructions. Alarm actionmessages may change based on assigned user or location.

In embodiments, the gas detection instrument may feature audible,visual, and/or vibrating alarm indicators that may be used in multiplemodes. For example, the audible indicator may be capable of delivering atone at a programmed decibel level, in embodiments, 95 dB, at a pre-setdistance. In another embodiment, output could be visual such theflashing action of four ultra-bright LEDs, of varying colors such as redand two blue, may attract the attention of the user and others around.In yet another embodiment, a vibrating alarm may provide a tactile alertto the user in the highest noise environments.

In embodiments, the device 1508 or instrument 108/110 may execute anapplication that is programmed to utilize the assignment data, such asuser identification and location or other information programmed to theassignment tag, to trigger alarms and/or messages, or filter thetriggers. The application may be updated periodically by the server 130,such as to modify variables that will cause a trigger at particularlocations or relationships concerning worker variables and alarmtriggers. For example, at one particular location, detection of aparticular gas may not be cause for alarm, however, at another locationwhere conditions may be different, the same gas at the same detectedconcentration may be concerning or dangerous. For example, methanedetected at a particular level may trigger an alarm and/or message at alocation where ignition sources are present but cause no triggers atlocations where it is known that no ignition sources are present. Inanother example, the gas detection instrument may only trigger a highcarbon monoxide alarm if the user assigned is above a certain weight.

As discussed herein, data transmitted through the gateway 112 or adevice to a remote location may be used in various end applicationseither by itself or in conjunction with other data, other devices, otherinformation or the like. Any number of applications of the worker safetysystem may be imagined, a number of exemplary applications will bedescribed herein.

In one example, data from instruments 108, 110 or other nodes may beused for continuous safety inspections. Limits for particular measuredvariables may be set for individuals and/or groups in respect ofautomated, real-time, monitoring of safety parameters. The worker safetysystem may issue warnings when limits are approached to the appropriateaudience.

In one example, data from instruments 108, 110 or other nodes may beused for lone worker monitoring. For example, if a lone worker's devicetriggers an alarm, such as a gas alarm, the connectivity of theinstrument to a smart device, such as via an API 114, allows for thatalarm to be detected remotely. Remote detection of an alarm may allow asupervisor, for example, to check-in on the lone worker or be able tosend help as needed.

In an example, data transmitted to the cloud from instruments 108, 110may be used for e-permitting. Certain confined spaces cannot be enteredwithout first sampling the environment in the confined space, thus asampling device may need to be present. Typically, permitting to enterthe confined space is done using manual data entry to apply for apermit. The disclosure herein enables the same device that collects dataon the environment of the confined space to transmit that data to anelectronic permitting application for use in applying for a permit toenter the confined space. In embodiments, the device 118 may be aruggedized tablet with an integrated gas sensor or with a connection toan instrument 108, 110 that provides gas sensing, wherein the senseddata are automatically provided to auto-fill an onboard application ortransmitted to the cloud for use in an application, and in embodiments,is auto-submitted to the relevant permitting authorities.

In an example, data transmitted to the cloud from instruments 108, 110may be coordinated with third party data. For example, additionalhazards may be alarmed through the instruments 108, 110 by overlayinglocation data derived from the devices 118 or instruments 108, 110 withthird party data, such as NOAA data, news/threat/terrorist data, orother external/3^(rd) party data. Such a capability may be especiallyimportant for lone workers.

In an example, data transmitted to the cloud from instruments 108, 110may be used by fire responders and other first responders. In additionto SCBA data, data from environmental monitoring (e.g. gas data), can bedelivered automatically to fire responders (or other first responders)to provide site/all-in-one safety. The worker safety system may supportautomatically configured emergency nodes for first responders. Forexample, automatic configuration/pairing may occur for emergencyresponder use in a monitoring group. In embodiments, separate indicatorsmay be used for responder-worn nodes

In an example, data transmitted to the cloud from instruments 108, 110and various safety devices may be used by the worker safety system inthe personal monitoring of various physiological and/or behavioralattributes of an individual in order to obtain information relevant toworkplace safety, or to alert nearby users regarding a workplace safetysituation. Thus, the worker safety system provides a remote and localbiometric monitoring interface with nodes in the ad-hoc P2P or meshnetwork. A user-worn node has an interface to a worker to monitorphysiological and/or behavioral attributes. The measured biometriclevels are used for remote monitoring and alarms. The goal of suchmonitoring may be to determine the root causes and acute symptoms ofdeath and injury in the workplace and mitigate the risk of death in theworkplace or other major accidents and exposures, such as injury fromfires or explosions, exposure to harmful substances or environments,falls, slips, trips, contact with objects and equipment, assaults andviolent acts, suicide, terrorism, transportation incidents,overexertion, repetitive motion, and the like. A further goal may be todetermine and understand the physiological and behavioral effects of theroot causes and acute symptoms of death and injury in the workplace. Theworker safety system may be useful in various industries, such as inmines, diesel/fuel plants, refrigeration, fertilizer plants, food &beverage, firefighting, chemical processing & manufacture, HazMat,medical, law enforcement, insurance, and the like.

Illustrative physiological markers may include ECG, heart rate,breathing rate, skin temperature, posture, activity, accelerometry,blood pressure, pulse, body odors, blood alcohol level, glucose levels,oxygen saturation, and the like. Illustrative behavioral markers mayinclude gait, walking patterns, eye movements, motion patterns, noises,removal of the sensor from the person before a prescribed time, and thelike.

Physiological and/or behavioral attributes may be measured by sensors,such as sensors integrated with instruments 108, 110, sensors located onthe body of an individual, clothing, and/or devices worn or used by theindividual. In embodiments, various sensors may be used to measure aperson's physiology and behavior, such as one or more of heart ratesensors, blood pressure sensors, gait detection sensors, olfactorysensors, galvanic skin response sensors, proximity sensors,accelerometers, eye tracking sensors, cameras/image sensor, microphones,infrared sensors, gas sensor, capacitive sensor, fingerprint sensor,signal detectors (e.g. WiFi, Bluetooth, mobile phone, etc.), locationdetectors (e.g. GPS sensor), and the like.

The physiological and/or behavioral attribute information may be used togain insight into the characteristics of an individual, a department, ora category of employee that may have an effect on the safety and workingconditions thereof. For example, the worker safety system may obtaindata for an individual to obtain a day-to-day baseline and may comparecurrent information to the baseline information. In another example, theworker safety system may compare an individual's information with a poolof data or with co-workers in a similar situation. The worker safetysystem may obtain and analyze the physiological and/or behavioral datato determine the physiological state of an individual (e.g., understress, fatigued, etc.), the causes of accidents in the workplace, or tomake predictions about workplace accidents. The worker safety system mayutilize sensed data and algorithmic output to provide intervention tothe individual or other interested parties (e.g. after two “nearmisses”, a supervisor is alerted and re-training may be scheduled), toblock a user from being able to access certain systems (e.g. afterdetecting a change in gait coupled with a temperature change, a signalis sent to nearby heavy machinery to block access to the individual), toallow a user to access systems (e.g. this individual was blocked becauseof flu but their temperature is now normal), to suggest behavioralchanges to avoid an accident (e.g. after eye tracking indicates fatigue,the user is signaled with a suggestion to take a break), and the like.The collected data may go into a pool of data that can be used forsubsequent comparisons.

The worker safety system may use the human body, such as humanphysiology and human behaviors, as a safety sensor or monitor to detecthazards including various sensors to measure a person's physiology andbehavior, and then make use of data from a person or group of people,both physiological and behavioral, of data algorithms to identify asafety issue, and of the data from a person or group of people toprevent accidents or fatalities using certain physiological orbehavioral markers. In embodiments, sensors deployed to obtain humanphysiology and human behaviors may form a body area network.

In embodiments, the use of data from a person or group of people, bothphysiological and behavioral, may be used to predict an accident,workplace injury, incident, “near miss”, etc.; determine if a person isin danger; determine if the environment is hazardous; identify thehazard or family of hazards; make judgments about the safety of aperson, group of people or the environment; alert the person, group ofpeople or someone who will intervene via visual, audible, haptic alarmsand the like; determine if the person is at risk of a future accident(including the use of near miss data); look for known patterns or toidentify new patterns related to personal safety, and the like.

In embodiments, the use of data algorithms may be used in the followingways to identify a safety issue: compare a person against themselves innear time or in historical time; compare the person against the datafrom a population; compare the data from one person to others workingwith them at that point in time, and the like.

In embodiments, use of the data from a person or group of people may beused to prevent accidents or fatalities using physiological orbehavioral markers. For example, at least one of heart rate, eyelidclosures, pupil size, blood pressure, posture, jaw drop, breathing rate,ECG, skin temperature, and sweat may be used as markers to preventaccidents or fatalities in the field of transportation. In anotherexample, at least one of gait, acceleration, blood pressure, heart rate,breathing rate, and posture may be used as markers to prevent accidentsor fatalities in the field of contacts with objects or equipment. Inanother example, at least one of gait, acceleration, blood pressure,heart rate, breathing rate, posture, ECG, sweat, and skin temperaturemay be used as markers to prevent accidents or fatalities in the fieldof slips, trips or falls. In another example, at least one of gait,acceleration, blood pressure, heart rate, breathing rate, posture, ECG,sweat, and skin temperature may be used as markers to prevent accidentsor fatalities in the field of exposure to harmful substances. In yetanother example, at least one of blood pressure, heart rate, breathingrate, posture, ECG, sweat, and skin temperature may be used as markersto prevent accidents or fatalities in the field of assaults or violence.In still another example, at least one of gait, acceleration, bloodpressure, heart rate, breathing rate, posture, ECG, sweat, and skintemperature may be used as markers to prevent accidents or fatalities inthe field of fires or explosions.

In embodiments, a database of sensor readings may be used to determinethe appropriate prediction or identification of the safety issues andthe appropriate response. The sensor readings may be wirelesslytransmitted to a computer, instrument 108/110, or device 118 andprocessed in near real time or real time to provide information andinsight regarding safety and hazard issues. The database may beconsulted for matching sensor readings and matching combinations ofsensor readings. Each combination of sensor readings may be associatedwith one or more particular safety issues and may be associated with oneor more particular responses. The safety issue and/or response may befurther limited by an additional factor, such as a supervisor oradministrator preference, a facility preference, a location, a user, acontext, a season, or a business rule. In an aspect, a method of thedisclosure may include obtaining sensor data from one or morephysiological and behavioral sensors worn by a user 1602, analyzing thesensor data to identify a safety issue 1604, and providing an alert tothe user or an interested party regarding the identified safety issue1608. Analyzing may include matching the sensor data to a knowncombination of sensor readings in a database of sensor readingcombinations. In an embodiment, an application resident on theinstrument 108/110 or device 118 may determine a condition hazardous tosafety based on the sensor readings and algorithms to determine if thereadings are indicating of a root cause or acute symptom of an incident.If a root cause or acute symptom is identified, an alert may begenerated and sent through the instrument/device via the wirelessnetwork 104 to alert other users and ultimately on to the server 130. Inembodiments, the transmitted information may be used to de-authorize theuser from an area or equipment, deploy personnel, remotely close off anarea, request a check-in on the user, and the like.

In embodiments, when certain physiological markers are combined withcertain behavioral markers in a known pattern, a condition may bedetermined and an alert or response may be elicited. In one example,when a person falls or almost falls, physiological markers of thecondition may include the heart speeding up, blood pressure rising,sweating, lungs breathing faster, and the temperature in the extremitiesmay decrease. Behavioral markers of the condition may include a noisebeing made, a sudden acceleration then a period of not moving, and thelike. These markers taken together may form a pattern indicative of afall or an almost fall.

In another example, when an individual is sleep-deprived, physiologicalmarkers of the condition may include increased heart rate, increasedblood pressure, and reduced leptin levels. Behavioral markers of thecondition may include increased eyelid closure, eyes rolling, andyawning.

Table 1 indicates various incidents and their possible root causes oracute symptoms. When text is present in the cell, it is an indicationthat there is a correlation between the incident and the possible rootcause or acute symptom. In some embodiments, there may be a temporalaspect to the correlation, such as if the root cause or symptom can bemeasured prior to the incident (Before), after the incident (After), orboth (Both). In some instances, a simple correlation (Correlated) isindicated. The cells in Table 1 are blank if no correlation is currentlyknown.

TABLE 1 Root Causes or Acute Symptoms of Incidents Exposure to RootCauses or Falls, Harmful Acute Contact with Slips, Substances/ Fires andSymptoms Transportation Violence Objects/Equipment Trips EnvironmentsExplosions Acute Stress Both Both Fatigue Before Under influence BothCorrelated Both (Drugs/Alcohol) Distracted Before Correlated ExcessiveBefore Speed Equipment Correlated Failure Weather Correlated BeforeBefore Aggressive Correlated Anger Both Fear After After Awkward GaitBoth Injury Before Old age Both Inadequate Before traction Speed ofBefore movement Light/Dark Before Before Temperature Before Before

With respect to fatigue, markers including heart rate, blood pressure,eyelid closures (slow closures, frequency of closures), pupil size, headposition, and jaw drop, as well as other cardiovascular disturbances andsympathetic activity may be used to identify the condition.

With respect to stress, markers including heart rate (e.g. increasedheart rate), sweat, dilated pupils, shallow breathing, increased bloodpressure, changes in a person's voice (pitch, rate, volume), odor andtightened scalp may be used to identify the condition.

With respect to being under the influence, markers including breathingrate, increased blood pressure, increased heart rate, gait and speechchanges may be used to identify the condition.

With respect to anger, markers including jaw clenching/teeth grinding,headache, stomachache, increased blood pressure, increased breathingrate, increased heart rate, sweating (especially hands), feeling hot inthe neck/face, shaking/trembling, and dizziness may be used to identifythe condition.

With respect to slips, trips, and falls, markers including breathingrate, blood pressure, heart rate, and awkward gait may be used topredict or identify a slip, trip, or fall. For example, the pattern forfear of heights, which is an indicator of potential falls, may be heartrate increase, stress temperature decrease, and systolic BP increase.However, if the situation includes an activity, such as climbing aladder which might increase the heart rate independently, then adding agait measurement may be necessary to determine if the individual is inmotion or not.

With respect to carbon monoxide exposure, markers including nausea,vomiting, restlessness, euphoria, fast heart rate, low blood pressure,cardiac arrhythmia, delirium hallucinations, dizziness, unsteadygait/stumbling, confusion, seizures, central nervous system depression,unconsciousness, respiratory rate changes, and respiratory arrest may beused to identify the condition.

Table 2 depicts how various physiological markers are associated withparticular root causes or symptoms.

TABLE 2 Part 1. Physiological Markers of Root Causes or symptoms. RootCauses or Acute Heart Blood Breathing Pupil Size Shaking/ Symptoms RatePressure Sweat Rate Gait Change Trembling Dizzy Acute Stress X X X X X XX Fatigue X X X X X Under X X X X X X X influence (Drugs/Alcohol)Distracted Excessive Speed Equipment Failure Weather X X X X AggressiveAnger X X X X X X Fear X X X X X Awkward X X Gait Injury X Old age XInadequate X traction Speed of X movement

TABLE 2 Part 2. Physiological Markers of Root Causes or symptoms. Headposition, Root Causes Hot/flushed facial or Acute Stomach- Head- face &Body O2 Eye changes, jaw Voice Symptoms ache ache neck Temp Level OdorBlinks drop changes Acute Stress X Fatigue X X X X X Under X X Xinfluence (Drugs/Alcohol) Distracted Excessive Speed Equipment FailureWeather X X X Aggressive Anger X X X Fear X X Awkward Gait Injury Oldage Inadequate traction Speed of movement

In embodiments, the systems and methods for monitoring physiology andbehavior to identify or predict safety issues and mitigate risk may beembodied in a wearable device. In embodiments, the wearable device mayinclude multiple physiological or behavioral sensors, such as thosedescribed herein. In embodiments, the wearable device may be a garmentwith one or more embedded sensors, a watch, a portable device, a badge,eyewear, a ring, and the like. The wearable device may include awireless transmitter to transmit data in the manners described hereinand ultimately to a server for analysis. The device may include adisplay to present content from a server based on analyzed data. Thecontent may be information or an alert. The garment may be a vest,hardhat, jumpsuit, belt, band, and the like.

In embodiments, simulation software may be built on data modelsdeveloped after a period of data collection on personal monitoring. Thesimulation software may have input variables, such as behavioral,mechanical, environmental, and physical, and risks may be identified. Inone example, the input variable may be a piece of personal protectiveequipment and a simulated work environment and risk factors may beidentified.

In embodiments, software application resident on a device, such as aninstrument 108, 110, safety device, mobile device, or the like, mayoverlay safety concerns on a real time view of the surroundingenvironment using augmented reality. Safety concerns can bepre-identified or can also be identified in real time.

In an embodiment, certain behaviors may be rewards and incentivesoffered to workers who do the right thing safety/compliance-wise basedon analysis of collected data. For example, if the data collectionindicates that the worker fell and then checked in to the nurses' officewithin a set period of time, they may be rewarded with a meal voucher orthe like. Rewards may be given for other compliant behavior, such aschecking an instrument back in to a tool crib, tagging instrument datawith a location-based NFC tag, wearing PPE correctly, checking in withanother worker, and the like.

Commercially available wearable devices useful in the disclosed systemsand methods include devices such as the Zephyr BioHarness™, AframeDigital MobileCare Monitor, BodyMedia FIT, Nonin, Valencell Performtek,Gaitometer, Wahoo Strap Monitor, Stress Thermometer, and others.

Continuing with another example of an application of the worker safetysystem, an application, which may be executing on instruments 108/110,devices 118, the server 130 or on a third party device, may prepare adynamic map view of node location in the ad-hoc P2P or mesh network tomonitor and display one or more node locations. The map may displayrelative location without reference to an area map, absolute locationwith reference to an area map, or 3D location on a topographic map ortunnel system. The map view may present alarm locations. In embodiments,a plurality of instruments 108/110, which may be enabled to communicatein the wireless network 104 or may be NFC-enabled, may transmit data(e.g., sensed data, assignment data, location data, calibration status,etc.) to the server 130, at least partially transmitted by the wirelessnetwork 104, wherein the data may be further displayed in the map view.

Continuing with another example of an application of the worker safetysystem, real-time information signage may be used in conjunction withdata collected from instruments 108, 110. For example, a real-time signmay be in electronic communication with one or more instruments 108/110,devices 118, the server 130 or a third party device such as by WiFi,Bluetooth, RFID or the like The real-time sign may be located in an areaand may display data based on an alarm from a nearby instrument 108, 110and may serve as a remote alarm. The data may be transmitted directly tothe sign using the wireless network 104 or may be transmitted to thecloud where it is processed to determine if it should be displayed onthe real-time information sign. In embodiments, a plurality ofinstruments 108/110, which may be enabled to communicate in the wirelessnetwork 104 or may be NFC-enabled, may transmit data (e.g., sensed data,assignment data, location data, calibration status, etc.) to the server130, at least partially by the wireless network 104, wherein the datamay be displayed by the real-time sign.

In another example of an application of the worker safety system, datacollected from instruments 108, 110, such as noise dosimeters, may beused to alarm workers. For example, if a gas detector tripped adetection threshold but a noise dosimeter indicated noise above acertain decibel range, the gas detector instrument will be signaled torelay its alarm via haptic and illuminated messaging as well as anaudible alarm. Further, the alarm message may also be displayed on anearby real-time informational sign.

In another example of an application of the worker safety system, datacollected from instruments 108, 110 may determine an amount of oxygen inthe environment. Under certain oxygen concentration conditions, acatalytic bead sensor may not work so the instrument may provide awarning. A remotely located supervisor may be alerted to the situationand deploy additional resources, such as personnel or different sensors,to the area to ensure safe and accurate monitoring.

In another example of an application of the worker safety system, datacollected from instruments 108, 110 may be used in combination totrigger various levels of alert/alarm. For example, if an instrumentreads a high carbon monoxide level, an alarm may be sounded but it mayonly be sounded at the instrument that made the reading. If aninstrument's accelerometer determines that a man is down, an alarm maybe sounded on the instrument as well as a few nearby instruments asdetermined by presence in the same wireless network 104 or proximity(e.g. GPS location, same NFC check-in to a location, manually identifiedlocation). If an instrument determines that both carbon monoxide is highand a man down is down, a critical alarm may be sounded on theinstrument, to nearby workers, and in a wide area.

In yet another example of an application of the worker safety system,the system may be used for leak detection/pipeline monitoring. Forexample, sensors for pipeline leak inspections for safety and compliancemonitoring, such as vehicle- or drone-mounted gas detectors, thermalconductivity or IR sensors, optical sensors, underground sensors, gasutility instruments and the like used to detect leaks may transmit datato the cloud or other remote location directly or through a device 118or gateway 131, 112. In this example, the drone may be operated remotelyin a two-way fashion so that control can be done locally or, forexample, if the area needs to be evacuated, control can be remote.Applications may use the data to remotely configure the sensors andmaintain the status of the sensors.

In still another example of an application of the worker safety system,the system may obtain data from eye wash stations, chemical showers,first aid stations, AED/defibrillator, fire extinguishers, sorbentstations or other fixed assets 124. In one example of an eye washstation or chemical shower, sensors may be placed at the station/drainto detect hazards/toxins that are being washed off a user, wherein thesensors may communicate data back to the cloud or remote location by anycommunication method described herein, either directly or through adevice 118 or gateway 131, 112. In embodiments, the sensors may bestand-alone sensors with remote communications capability or may havelocal communications capability at a nearby dock or instrument thatfurther transmits the data. In any event, such information may be usedin an application used by first responders to determine whatequipment/personnel to deploy. The data may be combined with other databeing collected by the worker safety system that may be localized to thesame area through the use of a shared assignment (e.g. NFC tags) or aknown location (e.g. GPS or known fixed asset 124 fixed location).Continuing with this example, the drain sensor may determine particulartoxins and a sensor in a smoke detector may indicate an identity ofparticulates in the air from a fire, in addition to temperature andvisibility data. Images may also be captured from a nearby camera. Thesedata combined together may alert a first responder that not only isthere a fire, but it is a chemical fire and what the specific chemicalit is that has caused the fire. Second responders may also be alerted asto what the specific cleanup needs will be. Thus, without any on-sitepersonnel calling an emergency number and explaining the situation,first and second responders may have unprecedented situationalawareness.

Continuing with this example, secondary alarms may be generated from aneyewash/shower pull. An inventory of items in the area may be needed inorder to generate the secondary alarms, wherein the inventory is knownat the remote location so that it gets displayed to first and secondresponders upon the eyewash/shower pull or the inventory is gathered bya nearby instrument and transmitted remotely. The inventory may includeinformation such as strong acid present, tank of phosphine present,gases present, chemicals present, combination of gases and chemicalspresent, or any information that would be on a posted hazard placard.

Continuing with the example of fixed assets 124 contributing to theworker safety system, a nearby sensor or integrated sensor may be ableto transmit data regarding the kind of fire extinguisher that was usedduring a fire, such as a water, foam, dry powder, carbon dioxide, ABC,wet chemical, metal, and the like, or what kind of sorbent was utilizedfor a spill. Such information may be useful to a first or secondresponder in determining equipment and personnel to deploy.

Continuing with the example of fixed assets 124 contributing to theworker safety system, a sensor in area that sense an acid spill or otherlike hazard may transmit data back to a remote location for processing.Depending on the kind of hazard detected, instructions or informationmay be transmitted to devices in the area, displayed on a real-timeinformation signage, transmitted to responders, and the like. Forexample, directions to the nearest eyewash/shower may be transmitted toinstruments or real-time signage in the area upon sensing an acid spillor other hazard. If there are multiple hazards, the instructions may bespecific as to which station to go to if one or more have not beenmaintained or are already in use, which would be known from sensed dataat that location. Nearby instruments may also be informed of the hazard,of the activation of a nearby eyewash/shower station, or asked to checkin with the user of a nearby instrument or warned to stay away from anarea. When a first worker is asked to check in with a second worker,they may receive reminders of the request until the worker safety systemdetects that the workers are near each other or if some other proof ofcontact has been transmitted. For example, a voice print from the secondworker or an image of the second worker may be recorded with theinstrument or device of the first worker doing the checking.

Continuing with the example of fixed assets 124 contributing to theworker safety system, integrated sensors with an eyewash station orshower may be used to automate and accelerate periodic testing of flowrate, total volume, water temperature, salinity, pH, and the like, inrespect of safety inspections, compliance with local or federalrequirements, and to predict the need for maintenance. With theintegrated sensors in communication with the worker safety system,automated maintenance reminders may be delivered, automated records maybe created of testing results and technicians performing tests,automated certificates of compliance may be generated, performancestatistics may be gathered, and the like.

In embodiments, one component of the worker safety system is to performa job hazard analysis (JHA) and then apply the hierarchy of hazardcontrols. The specific job is analyzed to understand varioussafety-related aspects, such as an identification of tasks, anidentification of potential hazards (e.g. gas, electrical, chemical,thermal, noise, etc.), and the like. The worker safety system may havethe information about various tasks and known potential hazards and payperform an analysis to determine if the hazard can be eliminated fromthe task. If not, the worker safety system may recommend a way tomitigate the hazard. For example, certain controls may be used tominimize hazards, such as engineering/mechanical controls. Alteredbehavior such as through training, real-time signage as discussedherein, instructional messages, and the like may be used to minimizehazards. Administration (e.g. scheduling) may also be useful inminimizing hazards.

In embodiments, the worker safety system may determine, based on theidentified hazard and task, an appropriate PPE or other protectivetechnology (e.g. foam protection, hearing protection, fall, etc.) to useto minimize a hazard. The worker safety system, through use of connectedinstruments and devices may determine if the correct subtype of PPE wasultimately selected by the worker, if the selected PPE has beenmaintained, if the selected PPE has been donned or is otherwise in use,if the selected PPE is being used properly, and the like. For example, ajob may require use of an air purifying respirator that filters in achemical or mechanical way to block dust, fumes or gases. The workersafety system may recommend a disposable versus a re-usable/refillablerespirator based on the task, the worker safety system may determine ifthe re-usable respirator has been properly maintained, and based on apressure reading from the respirator, the worker safety system maydetermine that the respirator is in proper use. Further, the airpurifying respirator may be equipped with a sensor, such as an RFID. Ifthe worker safety system detects that a worker is in an area requiringthe PPE or has indicated that a task has begun requiring the PPE but theRFID is not detected by the worker's instrument, an alarm may sound.

In another example, the worker safety system may determine, based on theidentified hazard and task, that a self-contained breathing apparatus isrequired (SCBA). Sensors on the supplied air tank may be used todetermine quality, efficacy (e.g. filter-mounted sensor), pressure (e.g.hose- or mouthpiece-mounted sensor), operational status, and the like.The sensors may communicate with beacons, devices, instruments, gatewaysor directly to the cloud or other remote location. Based on the sensorreadings, the worker safety system can anticipate or predict maintenancebased on usage and operational status instead of on a schedule. Theworker safety system can store pressure test results for annualcertification. The worker safety system can help set up a replacementtank, if necessary.

In an embodiment, the worker safety system may determine, based on theidentified hazard and task, that fall protection is required, such as aharness, a self-retracting lifeline, rails/guards, retrieval equipment,and the like. A sensor attached to a worker or integrated in aninstrument that is with the user may be used to determine if the workeris in the air. Further, knowing that data, the worker safety system candetermine if the appropriate fall protection equipment has been checkedout by the worker, if that fall protection has been maintained if theydo have it on, if the protective equipment is being worn, and if theyare using it correctly.

Various gas monitors that may be used in the worker safety system mayinclude gas sensors (e.g. IR, (LED), LEL, catalytic bead,electrochemical, redundant gas sensors), humidity sensor, temperaturesensor (e.g. to determine heat stress), a wind sensor, a microphone, anaccelerometer (e.g. to measure lack of motion in order to furtherdetermine man-down, acceleration/deceleration to determine a fall),particulate sensor, a barometer, biometric sensors, phase, time offlight, signal strength, GPS or other location-sensing technology, apanic button (e.g. to sound a loud alarm, to transmit a signalremotely), NFC, Bluetooth, radio module, WiFi, integrated cellulartechnology, and the like.

In one mode, alarms may be triggered based on set thresholds, such asdetection of one or more particular gases or detection of a thresholdamount of gas. In another mode, the gas detection instrument may includea dedicated panic button. For example, an alarm may be sounded when thepanic button is pressed and held for 3 seconds. This may allow the userto alert others at the press of a button in the event of distress. Inanother mode, the gas detection instrument may be programmed with a mandown alarm. For example, if the instrument does not detect motion via abuilt-in accelerometer for a predetermined number of seconds, an alarmmay be triggered and teammates may be alerted. In yet another mode,alarms may provide an early warning below a low alarm set point. Forexample, when a gas concentration exceeds an Acknowledgeable Gas Alertset point, the instrument may activate the alarm indicators to alert theuser that she may be approaching a dangerous condition. The user mayneed to take preliminary or mitigating action, but can acknowledge andsilence the alert while she continues her work. If the conditionpersists beyond 30 minutes, the alert may be reactivated.

The portable environmental sensing device or gas detection instrumentmay include a rugged case design, featuring field replaceable externaldust filters to prevent clogs, plastic edges to prevent overmoldpeeling, plastic rails to reduce overmold tearing, a plastic ridge toprotect external sensor filters when facedown, and a recessed display toprotect from scratches.

Gas monitors useful in the worker safety system may be portable,free-standing, fixed, battery-powered, wall-mounted with fixed linepower, modular, and the like. In embodiments, each form factor mayenable different functions or capabilities of the gas monitor. Inembodiments, a modular gas monitor may take the form of a centralsensing unit that can engage with various form factors. For example, themodular gas monitor may be able to engage with a free-standing base, aslot in a wall to engage with line power, a robotic unit, a piece ofheavy equipment such as a bulldozer, crane, etc., and the like.

In engaging with a free-standing base, the central sensing unit may bedisposed in the base in a downward facing manner which protects it fromthe environment and allows substantially 360 degree access toenvironment. The free standing base may have a speaker to sound alarmsin an area. The speaker may be a piezo-based speaker that may beelectronically designed for intrinsic safety. The central sensing unitmay be designed with bumps or other engagement features on the surfaceof the modules to prevent them from sliding out of the base. Thereceiving portion of the base may be designed to interact with theengagement features.

In embodiments, the central sensing unit may emit a loud sound duringcalibration and during setup (e.g. 108 dB). There may not be anelectronic way to control the sound by operation or by regulation. Anaccessory component may be provided for placement over the audio outputto dampen the sound. The geometric shapes inside the accessory componentmay provide additional surface area to absorb the sound.

In embodiments, monitors useful in the worker safety system may be areamonitors, such as perimeter monitor (e.g. at the edge of refinery),dust/particulates monitoring, noise/sound level, gases/fugitiveemissions, chemicals/toxins, fence line monitoring (e.g. cordon off anarea), and the like. In an embodiment, mere placement of the areamonitors and establishment of a peer network, as described herein, maycause the auto-establishment of fence lines and perimeters.

While area monitors 110 themselves may sense an environmental parameterthat may trigger an alarm, sending of a communication, controllinganother device or system, and the like, area monitors 110 may receive areport from a device 108, such as through the wireless network 104, andsound an alarm that may be audible widely. Area monitors 110 may receivea report from a device 108 or other network node, such as through thewireless network 104, and send out a communication to other devices 108and monitors 110. Area monitors 110 may receive a report from a device108, such as through the wireless network 104, and control anotherdevice or system in response to the report.

Turning now to describing particular instruments that may be used in theworker safety system, one such instrument is a portable electrochemicalgas sensing apparatus 108, or badge reader.

Toxic and combustible gas sensing instruments are important devices formany industrial and other applications, such as for safety,environmental and emissions monitoring, quality and process control,clinical diagnostic applications, and the like. In general, suchinstruments are portable and include sensors that are sensitive andaccurate.

An instrument with an electrochemical sensor may be used to measure theconcentration of a specific gas. The basic components of anelectrochemical sensor include a working (sensing) electrode, a counterelectrode, and optionally a reference electrode. These electrodes aretypically enclosed in a housing and are in contact with a liquid orsolid electrolyte. The working electrode is typically on the inner faceof a membrane, such as Teflon, which is porous to gas, but impermeableto the electrolyte.

The gas to be detected diffuses into the sensor and through the membraneto the working electrode and electrolyte. The electrolyte may be anaqueous solution of an acid, an alkali, an ionic liquid, or a mineralsalt; examples are sulfuric acid, phosphoric acid, potassium hydroxide,lithium chloride, and lithium perchlorate. The electrolyte may also beof an organic type such as tetraethyl ammonium perchlorate (TEAP) in alow vapor pressure organic solvent. When the gas reaches the workingelectrode and electrolyte, an electrochemical reaction occurs; either anoxidation or reduction depending on the type of gas. For example, carbonmonoxide may be oxidized to carbon dioxide, or oxygen may be reduced towater. An oxidation reaction results in the flow of electrons from theworking electrode to the counter electrode through an electroniccircuit, such as a potentiostat circuit, and conversely a reductionreaction results in flow of electrons from the counter electrode to theworking electrode through the electronic circuit. This flow of electronsconstitutes an electric current, which is proportional to the gasconcentration. The potentiostat circuit may be a part of an electronicprocessing unit in the instrument, which detects and amplifies thecurrent and scales the output according to the calibration. Theinstrument may then display the gas concentration in, for example, partsper million (PPM) for toxic gas sensors or percent volume for oxygensensors. Because the volume of the electrolyte can change with time andwith environmental conditions, a reservoir chamber is usuallyincorporated into the sensor to provide additional amounts ofelectrolyte and/or to allow for expansion of the electrolyte in certainenvironments.

An LEL (lower explosive limit) sensing instrument detects that one ormore combustible gases are in the atmosphere. For flammable substances,there is a limit concentration of gas necessary for ignition. Below thislimit, a mixture of the substance in air cannot be ignited. This limitis called the LEL. One type of LEL sensor is a catalytic bead sensor,which is designed to protect against the combustion of gases in theatmosphere, rather than specifically detect a single combustible gas.The LEL of a substance is established by standardized methods, andtypically lies between 0.5 and 15% by volume. A catalytic bead sensormay include two measuring beads (called pellistors), each made of porousceramic material embedding a small platinum wire coil. The active(sensing) bead contains catalytic material, while the other one is areference bead and does not contain catalytic material. The beads may bematched and built into a balanced, resistive circuit, such as aWheatstone bridge. When a combustible gas comes in contact with thesensor, the active bead begins to burn the gas causing it to increase intemperature, with a resulting increase in the bead's resistance that isproportional to the gas concentration. The reference bead does not reactto the combustible gas so its temperature and resistance does notincrease. The imbalance in the circuit is then converted into a gasreading. Once calibrated with a particular gas, an LEL sensor willdisplay values assuming all gases in the environment are that oneparticular gas. If a sensor calibrated to methane detects another gas,the instrument will display LEL values assuming it is truly methane.Correlation factors are therefore used to translate a reading from theunits of the calibration gas to the units of a second gas.

A catalytic bead sensor instrument may also include a processing unit.The processing unit and sensor are typically enclosed within a rigidcasing or housing.

FIGS. 17-19 illustrate an exemplary gas sensing apparatus 1700 with ahousing 1702 and an electrochemical sensor embedded in the housing 1702,and which is configured to detect one or more gases such as oxygen,carbon monoxide, methane, and hydrogen sulfide, along with others. Inparticular, housing 1702 may comprise one or more portions 1702A, 1702Bthat may be formed by molded plastic or the like. When the apparatus1700 is assembled, the housing may be sealed. As shown, a depression1706 is formed on an exterior surface of the housing 1702A, with acentrally disposed raised platform 1710 (shown in FIGS. 18 and 19) inthe depression 1706 formed on the exterior surface of the housing.Depression 1706 is integral with portion 1702B and, in embodiments,results from the molding process giving rise to portion 1702B. Thedepression comprises perimeter sidewalls defining the boundary of thedepression. In embodiments where the depression 1706 is circular, thedepression comprises a circumferential perimeter side wall 1706A, 1706B(FIG. 18). The perimeter sidewall has two portions 1706A, 1706B in FIG.18, as FIG. 18 is depicting an embodiment with a stepped-out upperportion.

The raised platform 1710 may support an electrode stack 1712 of theelectrochemical sensor within the depression 1706. The depression 1706also forms a second reservoir 1708 (bounded by the outer diameter orperimeter of the raised platform and the bottom portion of the perimeterside wall 1706B in the embodiment shown in FIG. 18) for electrolyte ofthe electrochemical sensor. As best seen in FIG. 17, the depression 1706may be cylindrical in shape to support a generally cylindrical sensor,although other shapes may also be used to accommodate sensors of variousshapes. The sensor may include the electrode stack 1712 as well as theelectrolyte solution in the second reservoir 1708.

As seen in FIGS. 18 and 19, the depression 1706 may include a firstreservoir 1718 and a second reservoir 1708, which may aid in support ofthe electrode stack 1712. The second reservoir is adapted to hold anelectrolyte solution that is in fluid communication with the electrodestack 1712. A sensor top cap 1714 is sized to fit over the depression1706, where the cap may include a capillary hole that provides accessfor gas to enter into the electrode stack 1712.

The electrode stack 1712 may include at least one measuring electrode,at least one counter electrode, and optionally, at least one referenceelectrode, along with a gas permeable membrane for allowing gas to flowto the measuring electrode. The stack 1712 may include one or moreelectrolyte absorption pads between the electrodes to ensure that theelectrolyte remains in contact with the electrodes. The electrode stack1712 may also include various other components, such as separators forthe electrodes. For example, an exemplary electrode stack is shown anddescribed in U.S. Pat. No. 8,771,490.

Housing 1702 defines an interior space 1705. Depression 1706 extendsinto interior space 1705, 2005 but is separated therefrom by theinterior-space facing surface of the sidewall and interior-space facingsurface base. A printed circuit board assembly 1704 may be disposed inthe interior space 1705, along with a battery 1707 or other power sourcefor providing power to circuitry of the apparatus 1700. For example, theassembly 1704 may include circuitry such as a processing unit 1703 witha potentiostat circuit in order to convert signals from the sensor intoa gas concentration reading or other parameter related to gasconcentration exposure. Although not specifically shown, the electrodestack 1712 may be in electrical communication with processing unit 1703,such as being connected via wires. In embodiments, the gas sensingapparatus 1700 does not have a user display for display of gasconcentration readings. Instead, the gas sensing apparatus 1700 mayinclude an interface to enable communication of such readings to anexternal device, via Bluetooth protocol or the like, such as to anapplication on a mobile phone or other computing device.

The electrode stack 1712 may be in electrical communication with analarm, such as an audible alarm, a visual alarm, a vibrating alarm orthe like, wherein the alarm may be located in the interior space of thehousing, or may be wirelessly connected to the processing unit 1703. Analarm modality may be automatically triggered, such as through detectionof one or more particular gases, detection of a threshold amount of gas,or the like. An alarm or message may be provided when determinations aremade regarding various detected conditions, such as gas present (alert,low alarm, and high alarm), STEL (short-term exposure limit) reached,and TWA (time-weighted average) above a threshold. In embodiments, analarm modality may feature audible, visual, and/or vibrating alarmindicators that may be used in multiple modes. For example, an audibleindicator may be capable of delivering a 95 dB tone at a distance of 10centimeters. In another example, the flashing action of fourultra-bright LEDs, two red and two blue, may attract the attention ofthe user and others nearby. In yet another example, a vibrating alarmmay provide a sensory alert to a user in a high noise environment.

FIG. 20 illustrates an exemplary portable combustible lower explosivelimit (LEL) gas sensing apparatus 2000 with a housing 2002 and acombustible LEL sensor formed within the housing 2002. In particular,housing 2002 may comprise one or more portions that are assembledtogether. When the apparatus 2000 is assembled, the housing may besealed. As shown, a sensor depression 2006 is formed on an exteriorsurface of the housing 2002, with a chamber separator 2024 integrallyformed in the exterior surface to separate an active sensing bead 2022in one chamber and a reference sensing bead 2020 in another chamber ofthe depression 2006. Depression 2006 is integral with housing 2002 and,in embodiments, results from the molding process giving rise to housing2002. Similar to the embodiments shown in connection with FIGS. 17-19,the depression comprises perimeter sidewalls defining the boundary ofthe depression. In embodiments where the depression is circular, thedepression comprises a circumferential perimeter side wall.

The depression 2006 may be cylindrical in shape. A sensor flame arrestor2026 may be sized to fit over the depression 2006.

An exemplary combustible gas sensor that may be integrated with housing2002 may include a gas sensing element including an electric heatingelement, a first layer coated on the electric heating element andcomprising a precious metal catalyst supported on a porous oxide, theprecious metal catalyst catalyzing combustion of a combustible gas to bedetected by the sensing element, and a second layer overlaying the firstlayer, and comprising a catalytic compound capable of trapping gaseswhich poison the precious metal catalyst. The sensor may also include acompensating element comprising an electric heating element lacking acatalyst. The sensing element and the compensating element may beconnected to a processing unit, not shown, that may be constructed andarranged to detect changes in resistance of the sensing element andcompensating element and to provide a reading of the changes. Forexample, an exemplary LEL sensor with gas sensing element andcompensating element is shown and described in U.S. Pat. No. 7,007,542.Appropriate catalytic materials for the first and second layers mayinclude one or more of oxide-supported metal oxides supported on porousoxide supports; solid acids, preferably solid superacids; solid bases,preferable solid superbases; and metal-loaded zeolites and clays.

Housing 2002 defines an interior space 2005. Similar to the embodimentsshown in FIGS. 17-19, depression 2006 extends into interior space 2005but is separated therefrom by the interior-space facing surface of thesidewall and base. A printed circuit board (PCB) assembly 2004 may bedisposed in the interior space 2005, along with a battery (not shown)for providing power to circuitry of the apparatus 2000, and containing aprocessing unit. For example, circuitry may include the processing unit,such as with a Wheatstone bridge circuit in order to convert signalsfrom the sensor into an LEL sensor reading or other parameter related topotential gas explosion. Each of the beads may be in electricalcommunication with the processing unit, such as being connected viawires. In embodiments, the gas sensing apparatus 2000 does not have auser display for display of gas concentration readings. Instead, the gassensing apparatus 2000 may include an interface to enable communicationof such readings to an external device, via Bluetooth protocol or thelike, such as to an application on a mobile phone or other computingdevice.

The sensor may be in electrical communication with an alarm, such as anaudible alarm, a visual alarm, a vibrating alarm or the like, whereinthe alarm may be located in the interior space of the housing, or may bewirelessly connected to the processing unit. An alarm modality may beautomatically triggered according to detection of various conditions. Inembodiments, an alarm modality may feature audible, visual, and/orvibrating alarm indicators that may be used in multiple modes. Forexample, an audible indicator may be capable of delivering a 95 dB toneat a distance of 10 centimeters. In another example, the flashing actionof four ultra-bright LEDs, two red and two blue, may attract theattention of the user and others nearby. In yet another example, avibrating alarm may provide a sensory alert to a user in a high noiseenvironment.

The gas sensing apparatus 1700 or 2000 with housing 1702 forming part ofthe sensor and its construction provides several advantages, in that theoverall packaging size is reduced, the component count is reduced, andpotential failure modes are reduced, as compared to prior gas sensinginstruments. In embodiments, the apparatus 1700 or 2000 may not need auser display, in that communication such as Bluetooth may providedisplay capability to an external device. A battery for the apparatusmay have a year or more of battery life. The manufacturing costs for thedevice may be reduced such that the apparatus may be customerdisposable.

Other gas monitors may include gas sensors (e.g. IR, (LED), LEL,catalytic bead, electrochemical, redundant gas sensors), humiditysensor, temperature sensor (e.g. to determine heat stress), a windsensor, a microphone, an accelerometer (e.g. to measure lack of motionin order to further determine man-down, acceleration/deceleration todetermine a fall), particulate sensor, a barometer, biometric sensors,phase, time of flight, signal strength, GPS or other location-sensingtechnology, a panic button (e.g. to sound a loud alarm, to transmit asignal remotely), NFC, Bluetooth, radio module, WiFi, integratedcellular technology, and the like.

Gas monitors useful in the worker safety system may be portable,free-standing, fixed, battery-powered, wall-mounted with fixed linepower, modular, and the like. In embodiments, each form factor mayenable different functions or capabilities of the gas monitor. Inembodiments, a modular gas monitor may take the form of a centralsensing unit that can engage with various form factors. For example, themodular gas monitor may be able to engage with a free-standing base, aslot in a wall to engage with line power, a robotic unit, a piece ofheavy equipment such as a bulldozer, crane, etc., and the like.

In engaging with a free-standing base, the central sensing unit may bedisposed in the base in a downward facing manner which protects it fromthe environment and allows substantially 360 degree access toenvironment. The free standing base may have a speaker to sound alarmsin an area. The speaker may be a piezo-based speaker that may beelectronically designed for intrinsic safety. The central sensing unitmay be designed with bumps or other engagement features on the surfaceof the modules to prevent them from sliding out of the base. Thereceiving portion of the base may be designed to interact with theengagement features.

In embodiments, the central sensing unit may emit a loud sound duringcalibration and during setup (e.g. 108 db). Regulatorily andoperationally, there may not be an electronic way to control the sound.An accessory component may be provided for placement over the audiooutput to dampen the sound. The geometric shapes inside the accessorycomponent may provide additional surface area to absorb the sound.

In embodiments, monitors useful in the worker safety system may be areamonitors, such as perimeter monitor (e.g. at the edge of refinery),dust/particulates monitoring, noise/sound level, gases/fugitiveemissions, chemicals/toxins, fenceline monitoring (e.g. cordon off anarea), and the like. In an embodiment, mere placement of the areamonitors and establishment of a peer network, as described herein, maycause the auto-establishment of fencelines and perimeters.

In an embodiment, portable, compact systems for estimating heat indexmay include a temperature sensor, a humidity sensor, and one or moremicrophones. Portable detection equipment 108 and area detectionequipment 110, such as equipment useful in the worker safety system, maybe used in environments where heat may negatively affect the equipment,the equipment's user(s), or both. For detection equipment, it may beadvisable to monitor the environment to assure proper operation of theequipment and user safety. While a temperature sensor will provide someinformation, an estimate of the heat index may provide more insight intopotential heat-related impact on equipment and users.

Historically, combined data from temperature and humidity sensors havebeen used to calculate a heat index. In some systems, a vane anemometermay be used to calculate wind speed and the calculated wind speed may befactored into the calculation of heat index. However, vane anemometersmay be large, making it difficult to incorporate into pieces ofdetection equipment, potentially necessitating the need for a user tocarry multiple pieces of detection equipment.

FIG. 21 depicts a heat index estimation system 2110 which may include atleast two microphones 2102 and temperature and humidity sensors 2104 inelectrical communication with a microprocessor 2108 for calculating aheat index from the data provided by the microphones 2102 andtemperature and humidity sensors 2104. The components of the heatestimation system 2110, such as the microphones 2102 and temperature andhumidity sensors 2104, may be solid-state components for inclusion indetection equipment 2112. In embodiments, the microprocessor 2108 is acomponent of the equipment 2112, however, it should be understood thatthe system 2110 may also or instead include its own microprocessorand/or networking capability.

The heat index estimation system 2110 may be modular with respect to thedetection equipment 2112 for ease of incorporation, insertion and/orremoval without disassembly of the equipment 2112. Further, the system2110 may be modularly interchangeable with other modules of theequipment. The heat index estimation system 2110 may be integrallyincorporated into the detection equipment 2112. In embodiments, theability to utilize solid-state temperature and humidity sensors withsolid state microphones for estimating wind speed renders thecombination, embodied in the system 2110, capable of fitting inside thedetection equipment 2112 and capable of modularity with respect to thedetection equipment 2112.

In embodiments, the components of the heat estimation system 2110 may bethermally isolated from one another.

The detection equipment 2112 may include at least one of a portable orarea environmental sensing device, a portable or area gas sensor, aportable or area multi-gas detection instrument, a respirator, alighting device, a fall arrest device, a thermal detector, a flamedetector, and a chemical, biological, radiological, nuclear, andexplosives (CBRNE) detector.

The heat index estimation system 2110 may be located on a surface of thepiece of detection equipment 2112 (FIG. 22A) or located in a cavity ofthe piece of equipment that is open to airflow 2114 (FIG. 22B).

The two microphones 2102 may be located linearly in a direction of theairflow 2114. In embodiments, there may be at least one additionalmicrophone 2102 located non-linearly with respect to a line formed bythe placement of the other microphones 2102 (FIG. 23). The microphone(s)may be directly subjected to wind or may be at the bottom of a recessthat is subjected to wind.

The microprocessor 2108 may be electrically coupled to the microphones2102 and sensors 2104. The microprocessor 2108 may analyze signals fromthe microphones 2102 for temporal, amplitude, and frequency differencesto make a wind speed approximation, such as a maximum wind speed, aninstantaneous wind speed, an average wind speed, and the like. Forexample, the microprocessor 2108 may analyze differences between soundsthat arrive at each microphone to calculate the speed of wind across oneor both of the microphones. In embodiments, one microphone may beshielded. Algorithms may be used to analyze the noise from a microphoneexposed to the wind and compare it to the noise from a shieldedmicrophone and to estimate wind speed. In embodiments, the algorithm maysubtract the signal of the non-shielded microphone to obtain a windcomponent without ambient noise. In embodiments, a time delay betweenone microphone and a second microphone is used to determine adirectional component of sound as a proxy for wind direction. In certainembodiments, a single microphone may be used and the wind velocity maybe estimated from the volume of the wind.

A heat index may be calculated using a polynomial equation with sensedtemperature and sensed absolute or relative humidity. The coefficientsin the common equations known to one skilled in the art are typicallybased on a variety of assumptions, including a wind speed ofapproximately 5 mph. Knowing if the wind speed was more or less than 5mph would enable the device to alert the user appropriately.

In some embodiments, a version of the system 2110 may not havemicrophones, and so would not use wind speed but could still provideheat index based on temperature and humidity data. This version of thesystem 2110 may also be modular with respect to the equipment 2112 andsized to be able to fit inside the equipment 2112. In embodiments, datafrom the humidity sensor, which may include relative and absolutehumidity, may be used for sensor compensation.

In embodiments, the heat index information may be provided to a user ofthe detection equipment 2112, optionally along with guidelines forself-protection based on the calculated heat index. For example, if acalculated heat index reaches a threshold, the equipment 2112 maytrigger an alarm on the equipment 2112 and any other nearby devices ornetworked devices or systems. The alarm may be audible, visual, hapticor any combination thereof. Self-protection guidelines may be displayedon the equipment or transmitted through a speaker of the equipment orother devices or system. Optionally, the calculated heat index maytrigger a communication to the user and/or other interested party, suchas a communication, call, message, and/or email. The communication mayinclude a warning and/or self-protection guidelines.

Turning now to describing particular improvements to environmentalsensing devices 108,110, such as those that may be useful in the workersafety system, one such improvement relates to the use of a baselineauto-matching circuit for an LEL sensor.

Combustible gas detectors have been widely used in industry to detectand monitor the presence of combustible gases or vapors for safety andenvironmental purposes. They can provide an early warning of potentiallyexplosive conditions to protect life and property before onset of ahazardous situation.

Multiple gas sensing technologies may be used in such gas detectors suchas thermal conductivity sensors, infrared (IR) sensors, semiconductor(MOS) sensors and catalytic bead (or pellistor) sensors. Among these,catalytic bead sensors are most commonly used due to their low cost,high performance and wide coverage of target gases. A catalytic beadsensor typically contains two ceramic beads coated onto metal, such asplatinum, wire coils, a sensing bead and a compensating bead. Thesensing bead may be impregnated with a noble metal catalyst, whichpromotes combustion of the combustible gases or vapors, while thecompensating bead may not contain a catalyst, but compensates forenvironmental effects such as humidity and ambient temperature changes.

There are multiple ways to configure the circuit of the two beads. Manycommercial combustible gas detectors are based on a Wheatstone bridge2400, an example of which is shown in FIG. 24 and described in U.S. Pat.No. 4,313,907. When an input voltage 2401 is applied across the bridge,resistive heating of the platinum wire coils and hence the beads 2402,2404 takes place. In the presence of a combustible gas or vapor,catalytic combustion takes place on the sensing bead 2402 and generatescombustion heat, causing an increase in the sensing bead 2402temperature relative to the temperature of the compensating bead 2404and, thus, the sensing bead 2402 wire resistance is increased relativeto that of the compensating bead 2404. The increased resistance of thesensing bead 2402 generates the differential output signal 2412 betweenthe two circuit branches, which is proportional to the gas concentrationin a given measurement range.

When a gas detector is manufactured, the combustible gas sensor baseline(differential voltage output when there is no combustible gas present)is typically tuned to be close to zero by selecting two matched beadswith close impedance. When the detector is deployed for field use, thebaseline may drift over the lifetime due to aging effects of the sensingbead 2402 and compensating bead 2404. FIG. 25 shows a graphic example ofa typical combustible catalytic bead gas sensor's span reserve 2502 (orsensitivity) and its baseline (mV) 2504 change over a period of time.

The term Span Reserve harkens back to the days when gas monitoringinstruments were driven by analog circuits and calibration was performedby adjusting the Zero and Span potentiometers. In that era, gas wasapplied to the instrument and the “span pot” was adjusted until thereading on the display matched the concentration of the gas being used.If you wanted to see how much life was in your sensor, you would turnthe span potentiometer up all the way and the subsequent reading wouldshow you how much reserve sensitivity was in the sensor or how much roomfor adjustment there was before the sensor could no longer becalibrated.

FIG. 25 depicts the baseline voltage slightly above zero mV at thebeginning of the depicted time period and decreasing over the measuredtime to approximately negative 18 mV at the latest stage of lifedepicted. Prior art approaches to address this issue includeauto-zeroing with software in gas detectors. However, this approachresults in a corresponding loss in the span reserve 2502 (sensitivity)as shown by the reduction of span reserve shown in FIG. 25 fromapproximately 155% down to 120% over the same time period. Thus,auto-zeroing obscures the issue and does not resolve it, allowing theWheatstone bridge to continue becoming more unbalanced over time.

Thus, there remains a need for balanced bridge circuit configurationsfor combustible gas detectors that can maintain span reserve(sensitivity) over time.

FIG. 26A depicts a balanced bridge circuit 2600 having two branches,each connected in parallel with a power source 2601. The first branch2620 has a sensing bead R1 2602 and a compensating bead R2 2604connected in series. Sensing bead R1 2602 is further connected inparallel with a variable resistor R5 2608 and compensating bead R2 2604is further connected in parallel with a variable resistor R6 2612. Thesecond branch 2622 has a standard resistor R3 2610 and a standardresistor R4 2614 connected in series. A differential output meter 2618measures the baseline voltage and is disposed between the first branch2620 and the second branch 2622 with one side connected between thesensing bead 2602 and the compensating bead 2604 and the other sideconnected between the standard resistors 2610, 2614. This configurationmay enable any unbalance of the circuit due to changes, such as aging orother deterioration, of the sensing bead R1 2602 or compensating bead R22604 to be adjusted by varying one of the variable resistors R5 2608 orR6 2612 where the variable resistor adjusted may be selected based onthe degree of drift in bead R1 2602 relative to drift in bead R2 2604 soas to maintain the baseline as indicated by differential output meter2618 reading close to zero mV. In this and the following circuits, it isunderstood that the location in the circuit of the sensing bead R1 2602and the compensating bead R2 2604 may be switched.

In other embodiments, a single variable resistor may be used as shown inFIGS. 26 B-26 C. Referring to FIG. 26 B, a balanced bridge circuit 2630is depicted having two branches connected in parallel with a powersource 2601. The first branch 2626 has a sensing bead R1 2602 in serieswith a compensating bead R2 2604. Sensing bead R1 2602 is furtherconnected in parallel with a variable resistor R5 2608. The secondbranch 2627 has a standard resistor R3 2610 connected in series withresistor R4 2614. A differential output meter 2618 measures the baselinevoltage and is disposed between the first branch 2626 and the secondbranch 2627 with one side connected between the sensing bead 2602 andthe compensating bead 2604 and the other side connected between standardresistors R3 2610 and R4 2614. The value of variable resistor R5 2608may be adjusted to compensate for changes in the resistance of sensingbead R1 2602. This solution works if the value of sensing bead R1 2602is higher than that of compensating bead R2 2604. Otherwise, the circuitmay not be able to adjust the balance point given that the parallelconnection will only reduce the total resistance.

Referring to FIG. 26 C, a balanced bridge circuit 2640 is depictedhaving two branches connected in parallel with a power source 2601. Thefirst branch 2628 has a sensing bead R1 2602 and a compensating bead R22604 connected in series. Compensating bead R2 2604 is further connectedin parallel with a variable resistor R6 2612. The second branch 2629 hastwo standard resistors R3 2610 and R4 2614 connected in series. Althoughtwo resistors are shown more than two may be used. A differential outputmeter 2618 measures the baseline voltage and is disposed between thefirst branch 2628 and the second branch 2629 with one side connectedbetween the sensing bead 2602 and the compensating bead 2604 and theother side connected between the standard resistors 2610, 2614. Thevalue of variable resistor R6 2612 may be adjusted to compensate forchanges in the resistance of compensating bead R2 2604. The use of asingle variable resistor may save cost on hardware relative to the twovariable resistor embodiment of FIG. 26 A. This solution works if thevalue of sensing bead R1 2602 is lower than that of compensating bead R22604.

Another embodiment of a balanced bridge circuit 2700 is depicted in FIG.230A. There are two branches connected in parallel with each other and apower source 2601. The first branch 2702 has a sensor bead 2602 and acompensating bead 2604 connected in series. The second branch 2704 hastwo resistors, R3 2610 and R4 2616 connected in series. As theresistances of the beads 2602, 2604 in the first branch 2702 change withage, the ratio of the resistors in the second branch 2704 may beadjusted to achieve the desired baseline. To achieve this, either R32610 or R4 2616 (as shown in FIG. 27A) may be a variable resistor. Adifferential output meter 2618 disposed between the two branchesmeasures a baseline voltage with one side of the meter 2618 connected tothe first branch 2702 between the sensor bead 2602 and the compensatingbead 2604 and the other side of the meter being connected to the secondbranch 2704 between the two resistors 2610, 2616. Whenever there is aneed to balance the bridge circuit, the variable resistor (R3 2610 or R42616) will be adjusted or “tuned” to compensate for the relative changesof the beads R1 2602 and R2 2604 branch. For example, if R3 2610 equals10K ohms and the power applied to the bridge is 3V, the simulatedbaseline resulting from tuning R4 2616 is shown in FIG. 27B. Referringto FIG. 27B, the baseline voltage 2708 is shown as a function of thevalue of variable resistor R4 2616. This configuration facilitatesadjusting the baseline voltage 2708 over a wide range by adjusting thevalue of the variable resistor R4 2616, enabling tuning the circuit toadjust for changes to the baseline by adjusting the value of variableresistor R4. However, this tuning circuit results in large changes inbaseline voltage 2708 for relatively small changes in the value ofvariable resistor R4 2616.

FIG. 28A illustrates another embodiment of a balanced bridge circuit2800. There are two branches connected in parallel with each other and apower source 2601. The first branch 2804 has a sensor bead 2602 and acompensating bead 2604 connected in series. The second branch 2808 hastwo standard resistors, R3 2610 and R4 2614. The second branch 2808 alsoincludes a variable resistor R5 2802, which may be connected in parallelwith either resistor R3 2610 or R4 2614 (shown). A differential outputmeter 2618 disposed between the two branches measures a baseline voltagewith one side of the meter 2618 connected to the first branch 2804between the sensor bead 2602 and the compensating bead 2604 and theother side of the meter being connected to the second branch 2808between the two resistors 2610, 2614. FIG. 28B shows a simulation of thebaseline voltage 2852 as a function of the value of variable resistor R52802 when it is in parallel with resistor R4 2614. This circuit mayenable fine-tuning of the baseline voltage over a portion of the rangeof the variable resistor R5 2802. The range over which the circuit maybe finely tuned varies depending on whether the variable resistor R52802 is in parallel with R3 2610 or R4 2614.

Instead of tuning on one side, FIG. 29A shows an embodiment of abalanced bridge circuit 2900 that may enable tuning on both sides. Thereare two branches connected in parallel with each other and a powersource 2601. The first branch 2906 has a sensor bead 2602 and acompensating bead 2604 connected in series. The second branch 2908comprises two terminals of a three-terminal variable resistor(potentiometer) R3 2904 forming the second branch. A differential outputmeter 2618 disposed between the two branches measures a baseline voltagewith one side of the meter 2618 connected to the first branch 2906between the sensor bead 2602 and the compensating bead 2604 and theother side of the meter being connected to the wiper 2902 terminal ofthe three-terminal variable resistor R3 2904 forming the second branch2908. In this way, by adjusting the wiper 2902 up and down, the secondbranch 2908 may be adjusted to match changes to the beads, R1 2602 andR2 2604. FIG. 29B depicts a simulation of the resulting change inbaseline differential output 2952 as the wiper 2902 is adjusted. Thisembodiment results in a linear tuning curve where the baselinedifferential output varies linearly with the adjustment of the wiper2902.

FIG. 30A shows another embodiment of a balanced bridge circuit 3000which is a variant of the embodiment of FIG. 29A. There are two branchesconnected in parallel with each other and a power source 2601. The firstbranch 3010 has a sensor bead 2602 and a compensating bead 2604connected in series. The second branch 3012 has a three-terminalvariable resistor 3002, which may be a digital potentiometer, connectedin parallel to standard resistors R3 2610 and R4 2614. The wiper 3004 ofthe three-terminal variable resistor 3002 may be connected between thetwo standard resistors R3 2610 and R4 2614. A differential output meter2618 disposed between the two branches measures a baseline voltage withone side of the meter 2618 connected to the first branch 3010 betweenthe sensor bead 2602 and the compensating bead 2604 and the other sideof the meter being connected between to the wiper 3004 of thethree-terminal variable resistor R3 3002 and between the two standardresistors R3 2610 and R4 2614. In this way, by moving the wiper 3004 upand down, the bridge may be adjusted to match the changes of beads R12602 and R2 2604. Considering the typical baseline drift of a catalyticsensor may be small, this circuit may enable accurate tuning. FIG. 30Bdepicts a simulation of the resulting change in baseline differentialoutput 3052 as the wiper 3004 is adjusted. In the middle range of thematching point, the tuning step is very fine. For example, assuming R32610 and R4 2614 is 10K ohms, R5 3002 is 100K ohms, and the power supply2601 is 3V, the adjustable baseline 3052 may be as small as 2 mV.

FIG. 31 shows an embodiment of a bridge circuit 3100 being balancedthrough a digital potentiometer and microprocessor in a gas detector.There are two branches connected in parallel with each other and a powersource 2601. The first branch 3110 has a sensor bead 2602 and acompensating bead 2604 connected in series. The second branch 3112 has athree-terminal digital potentiometer 3106, connected in parallel to twostandard resistors R3 2610 and R4 2614 connected in series. Adifferential A/D convertor is disposed between the two branches with theconnection to the first branch 3110 located between the sensor bead 2602and the compensating bead 2604. The connection to the second branch 3112is connected between the two standard resistors R3 2610 and R4 2614 tothe wiper 3108 of the digital potentiometer 3106. When the bridgecircuit is balanced, the differential output voltage detected bymicroprocessor 3104 through A/D convertor 3102 stays close to zero ifthere is no combustible gas present. When a significant baseline drifthappens, the differential output will become non-zero (above thetolerance range i.e. 10 mV) even if there is no combustible gas present.At this time, the instrument may send a command to digital potentiometerR5 3106 to change its position of wiper 3108 to match the new R1 2602/R22604 values until differential output voltage drops within a tolerancerange (i.e. 10 mV).

FIG. 32A depicts another embodiment of a balanced bridge circuit 3200which is a variant of the embodiment of FIG. 30A. There are two branchesconnected in parallel with each other and a power source 2601. The firstbranch 3210 has a sensor bead 2602 and a compensating bead 2604connected in series. The second branch 3212 has a three-terminalvariable resistor 3202, which may be a digital potentiometer, connectedin series between standard resistors R3 2610 and R4 2614, while thewiper 3204 terminal is connected to one side of a differential outputmeter 2618. The other end of the differential output meter 2618 isconnected to the first branch 3210 between the sensor bead 2602 and thecompensating bead 2604. In this way, by moving the wiper 3204 up anddown, the bridge may be adjusted to match the changes of beads R1 2602and R2 2604. Considering the typical baseline drift of a catalyticsensor may be small, this circuit may enable accurate and linear tuning.FIG. 32B depicts a simulation of the resulting change in baselinedifferential output 3252 as the wiper 3204 is adjusted. As depicted, thetuning steps are fine and linear over most of the range of tuning. Forexample, assuming R3 2610 and R4 2614 are 10K ohms, R5 3202 is 2K ohmswith 256 steps, and the power supply 2601 is 3V, the adjustable baseline3252 may be as small as 1.1 mV.

FIG. 33 depicts an embodiment of a balanced bridge circuit 3300 balancedthrough a digital potentiometer and microprocessor in a gas detector.There are two branches connected in parallel with each other and a powersource 2601. The first branch 3310 has a sensor bead 2602 and acompensating bead 2604 connected in series. The second branch 3312 has athree-terminal digital potentiometer 3302, connected between twostandard resistors R3 2610 and R4 2614. A differential A/D convertor isdisposed between the two branches with the connection to the firstbranch 3310 located between the sensor bead 2602 and the compensatingbead 2604. The connection to the second branch 3312 is connected to thewiper 3304 of the digital potentiometer 3302. When the bridge circuit isbalanced, the differential output voltage detected by microprocessor3104 through A/D convertor 3102 stays close to zero if there is nocombustible gas present. When a significant baseline drift happens, thedifferential output will become non-zero (above the tolerance range i.e.10 mV) even if there is no combustible gas present. At this time, themicroprocessor 3104 may calculate how much tuning resistance may beneeded to reduce the differential output and send a command to digitalpotentiometer R5 3302 to change its position of wiper 3304 to match thenew R1 2602/R2 2604 values. This tuning may be done in one step andbring down the baseline close to zero.

Continuing with describing particular improvements to environmentalsensing devices 108, 110, such as gas monitors, that may be used in theworker safety system, one such improvement relates to lead-free filtersfor catalytic bead sensors. Catalytic bead sensors used to detectcombustible gases may exhibit reduced sensitivity to certain combustiblegases such as methane, in the presence of catalyst poisons, such ashydrogen sulfide. The effect of hydrogen sulfide on the catalytic beadsensor may be ameliorated by the use of filters to remove the hydrogensulfide from the gas passing over the sensor.

There remains an ongoing need for methods for the manufacture of highlyefficient filters that do not contain lead.

The methods described herein produce metallic copper filters, whereinsome embodiments of the methods disclosed herein produce nanometer-scalemetallic copper particles. These may be in the range of 1-100nanometers. Particles on the nanometer scale may be highly reactive withhydrogen sulfide and may have a high surface area for reacting withhydrogen sulfide. Filters prepared using the methods described hereinhave a high capacity preventing the transmission of hydrogen sulfidethrough the filter. While porous glass fiber filters will be usedthroughout this specification as an exemplary substrate in theembodiments, it should be understood that other substrates may also beuseful in the embodiments of the disclosure, such as alumina, silica,zirconia, and titanium substrates. Indeed, in some embodiments, themetallic copper particles may themselves be used as the filter withoutany need for a supporting substrate.

In one embodiment, referring to FIG. 34, a metallic copper particlefilter may be made by preparing a solution of a copper compound (step3402), such as copper sulfate, copper chloride and the like and applyingthe copper solution to a glass fiber paper (step 3404). The glass fiberpaper coated with the copper compound may then be dried (step 3408) atroom temperature or at an elevated temperature. A second solution ofsodium borohydride may be prepared (step 3410) and applied to the glassfiber paper coated with the copper compound (step 3412) resulting in thecopper compound being reduced to metallic copper. The glass fiber papercoated with the metallic copper is then dried (step 3414) at roomtemperature or at an elevated temperature for use in the sensor.

In another embodiment, and referring now to FIG. 35, a metallic copperparticle filter may be made by preparing a solution of copper compound(step 3502) and applying the copper solution to a glass fiber paper(step 3504). The glass fiber paper coated with the copper solution maythen be dried (step 3508) at room temperature or at an elevatedtemperature. Hydrogen in nitrogen may then be applied to the glass fiberpaper coated with the copper compound (step 3510) resulting in thecopper compound being reduced to metallic copper particles.

In another embodiment, and referring to FIG. 36, a metallic copperparticle filter may be made by preparing a solution of a copper compound(step 3602), preparing a solution of sodium borohydride (step 3604), andmixing the two solutions (step 3608) resulting in the copper compoundbeing reduced to metallic copper particles. The metallic copperparticles may then be dried (step 3610) at room temperature or at anelevated temperature.

Since the copper particles are small in size, the filter color may beblack instead of bronze (color of copper large particles or pieces). Thecopper particles may form a porous material to effectively blockhydrogen sulfide.

As shown in FIG. 37, a graph comparing the capacity of differenthydrogen sulfide filters, in parts per million (ppm) Hours (hrs), isshown. The graph charts the capacity of a disclosed metallic copperfilter created using the method of FIG. 34 (800 ppm hrs) as well as alead acetate filter (1200 ppm hrs), a copper sulfate filter (531 ppmhrs), an iron chloride filter (40 ppm hrs), a zinc acetate filter (40ppm hrs), a copper chloride filter (40 ppm hrs), and a nickel chloridefilter (60 ppm hrs). The data in this graph can be interpreted asdemonstrating that the metallic copper particle filter and the coppersulfate filter, approach the capacity of the conventional lead acetatefilter.

The effectiveness of filters made using the methods described herein maybe seen in FIG. 38, a graph depicting the change in methane sensitivity(in mV/% LEL) of a sensor over time in an atmosphere having 25 parts permillion (ppm) of hydrogen sulfide. In the absence of a filter 3910, thesensitivity falls off quickly. However, the presence of a filter of leadacetate 3902 or metallic copper 3904 show very little fall off insensitivity over time spent in the presence of hydrogen sulfide. Afilter of copper sulfate 3908 provides some protection but there is anoticeable decrease in sensitivity relative to the metallic copperfilter 3904 and always remains below that of metallic copper.

Continuing with describing particular improvements to environmentalsensing devices 108, 110, such as gas monitors, that may be used in theworker safety system, one such improvement relates to mechanicalstability. Catalytic bead combustible gas sensors have been widely usedin industry to detect the presence of combustible gases and vapors forsafety purposes and to provide a warning of potentially hazardousconditions before these gases and vapors reach explosive levels.Commercial catalytic bead sensors detect gases through the use ofelectrically heated helical filaments typically embedded within acatalytic material. The mechanical stability of this assembly iscompromised by the weight of the catalytic material itself. Thus, thereremains a need for combustible gas sensors with improved mechanicalstability.

Referring to FIGS. 39A & 39B, a gas sensing or compensating element of acombustible gas sensor is shown. A cantilever support 4002 is connectedto a coated coil 4004 and attached to a third support post 4008. Thecoated coil 4004 is attached to two support posts 4010. The coated coilsis coated via chemical vapor deposition (CVD) with an insulatingmaterial that keeps the winds of the coil from touching and creating hotspots and prevents the cantilever support 4002 from shorting the coilturns electronically. In embodiments, the cantilever support 4002supports the wire that the coil 4004 is a part of, and may be connectedto the coil by soldering, but it is understood that other attachmentmethods are contemplated as well. In some embodiments, the cantilever4002 is disposed or threaded entirely through the coil 4004 and emergeson the other side of the coil, such as shown in FIG. 39A, while in otherembodiments, the cantilever 4002 is only partially disposed or threadedthrough the coil. In some embodiments, the cantilever 4002 supports thecoil 4004 from beneath, such as in FIG. 39B, or from above the coil. Thecoated coil 4004 is part of a resistance wire whose ends are attached tothe support posts 4010. While in some embodiments, the cantilever doesnot touch the coil, it is possible for the cantilever to touch the coilsince the coil is coated with an insulating material, such as in FIG.39C.

Referring to FIG. 40, a bead 4102 is fabricated to coat both thecantilever support 4002 and the coil 4004. The bead 4102 may be of acatalytic material or may be another material, such as ceramic, coatedwith or mixed with a catalytic material, such as platinum or palladium.In an embodiment, the bead 4102 may include an inner layer of a porousoxide-supported precious metal catalyst that catalyzes the combustionreaction, and an outer layer of a porous oxide-supported catalyticmaterial that effectively traps catalyst poisons. Formation of the bead4102 (either a sensing bead or a compensating bead) may occur by variousprocesses, such as those described in U.S. Pat. No. 7,007,542, which isincorporated by reference herein.

In operation, electrical currents are passed through the coil 4004causing it to become heated. Combustible gases that come in contact withthe catalytic material of the bead 4102 coating the coil 4004 maycombust at a lower than normal ignition temperature, causing furtherheating of the coil 4004 and a change in its electrical resistance whichis detected by sensor-associated electronics.

Adding a third support post 4008 to the gas sensing element enables useof the cantilever 4002 to mechanically support the excess weight of thecatalytic bead 4102 and also allow for a reduced coil wire size toreduce the power necessary to run the system. The cantilever 4002 may bethreaded through the center of the coil 4004 and is subsequently coatedtogether with the coil 4004 within the bead 4102 during beadfabrication, thus ensuring that the cantilever 4002 and the coil 4004are mechanically joined for more stable support.

By using only three support posts, fabricating the bead 4102 is moreconvenient with access to the entire open side (opposite the cantilever4002) of the coil 4004. Further, less power loss is observed when onlyrequiring one additional support as less additional operational power isrequired to overcome associated heat loss with three supports overdesigns that incorporate more than three supports. Mechanical stabilityof the assembly is greatly improved with the cantilever 4002 asexhibited by the results of durability testing, which may involvedropping an instrument containing the gas sensing element from one meteronto concrete. Without the cantilever 4002, the sensor withstands fewerdrops (e.g. eight) before malfunction or breakage, but with thecantilever 4002, the sensor can withstand numerous drops (e.g. greaterthan fifty-two). The cantilever 4002 also enables the use of very thincoil wire, such as 0.5 mil, to reduce the power necessary to run thesystem. Decreased wire diameter may result in higher resistance, andconcomitantly, a reduction in the sensor's overall electricalrequirements (power and current) in achieving a particular operatingtemperature. Such a reduction in power requirement may result inextending the life of the power supply or in enabling the furtherreduction of the size of the power supply.

The methods and systems described herein may be deployed in part or inwhole through a machine that executes computer software, program codes,and/or instructions on a processor. The processor may be part of aserver, client, network infrastructure, mobile computing platform,stationary computing platform, or other computing platform. A processormay be any kind of computational or processing device capable ofexecuting program instructions, codes, binary instructions and the like.The processor may be or include a signal processor, digital processor,embedded processor, microprocessor or any variant such as a co-processor(math co-processor, graphic co-processor, communication co-processor andthe like) and the like that may directly or indirectly facilitateexecution of program code or program instructions stored thereon. Inaddition, the processor may enable execution of multiple programs,threads, and codes. The threads may be executed simultaneously toenhance the performance of the processor and to facilitate simultaneousoperations of the application. By way of implementation, methods,program codes, program instructions and the like described herein may beimplemented in one or more thread. The thread may spawn other threadsthat may have assigned priorities associated with them; the processormay execute these threads based on priority or any other order based oninstructions provided in the program code. The processor may includememory that stores methods, codes, instructions and programs asdescribed herein and elsewhere. The processor may access a storagemedium through an interface that may store methods, codes, andinstructions as described herein and elsewhere. The storage mediumassociated with the processor for storing methods, programs, codes,program instructions or other type of instructions capable of beingexecuted by the computing or processing device may include but may notbe limited to one or more of a CD-ROM, DVD, memory, hard disk, flashdrive, RAM, ROM, cache and the like.

A processor may include one or more cores that may enhance speed andperformance of a multiprocessor. In embodiments, the process may be adual core processor, quad core processors, other chip-levelmultiprocessor and the like that combine two or more independent cores(called a die).

The methods and systems described herein may be deployed in part or inwhole through a machine that executes computer software on a server,client, firewall, gateway, hub, router, or other such computer and/ornetworking hardware. The software program may be associated with aserver that may include a file server, print server, domain server,internet server, intranet server and other variants such as secondaryserver, host server, distributed server and the like. The server mayinclude one or more of memories, processors, computer readabletransitory and/or non-transitory media, storage media, ports (physicaland virtual), communication devices, and interfaces capable of accessingother servers, clients, machines, and devices through a wired or awireless medium, and the like. The methods, programs or codes asdescribed herein and elsewhere may be executed by the server. Inaddition, other devices required for execution of methods as describedin this application may be considered as a part of the infrastructureassociated with the server.

The server may provide an interface to other devices including, withoutlimitation, clients, other servers, printers, database servers, printservers, file servers, communication servers, distributed servers andthe like. Additionally, this coupling and/or connection may facilitateremote execution of program across the network. The networking of someor all of these devices may facilitate parallel processing of a programor method at one or more location without deviating from the scope ofthe disclosure. In addition, all the devices attached to the serverthrough an interface may include at least one storage medium capable ofstoring methods, programs, code and/or instructions. A centralrepository may provide program instructions to be executed on differentdevices. In this implementation, the remote repository may act as astorage medium for program code, instructions, and programs.

The software program may be associated with a client that may include afile client, print client, domain client, internet client, intranetclient and other variants such as secondary client, host client,distributed client and the like. The client may include one or more ofmemories, processors, computer readable transitory and/or non-transitorymedia, storage media, ports (physical and virtual), communicationdevices, and interfaces capable of accessing other clients, servers,machines, and devices through a wired or a wireless medium, and thelike. The methods, programs or codes as described herein and elsewheremay be executed by the client. In addition, other devices required forexecution of methods as described in this application may be consideredas a part of the infrastructure associated with the client.

The client may provide an interface to other devices including, withoutlimitation, servers, other clients, printers, database servers, printservers, file servers, communication servers, distributed servers andthe like. Additionally, this coupling and/or connection may facilitateremote execution of program across the network. The networking of someor all of these devices may facilitate parallel processing of a programor method at one or more location without deviating from the scope ofthe disclosure. In addition, all the devices attached to the clientthrough an interface may include at least one storage medium capable ofstoring methods, programs, applications, code and/or instructions. Acentral repository may provide program instructions to be executed ondifferent devices. In this implementation, the remote repository may actas a storage medium for program code, instructions, and programs.

The methods and systems described herein may be deployed in part or inwhole through network infrastructures. The network infrastructure mayinclude elements such as computing devices, servers, routers, hubs,firewalls, clients, personal computers, communication devices, routingdevices and other active and passive devices, modules and/or componentsas known in the art. The computing and/or non-computing device(s)associated with the network infrastructure may include, apart from othercomponents, a storage medium such as flash memory, buffer, stack, RAM,ROM and the like. The processes, methods, program codes, instructionsdescribed herein and elsewhere may be executed by one or more of thenetwork infrastructural elements.

The methods, program codes, and instructions described herein andelsewhere may be implemented on a cellular network having multiplecells. The cellular network may either be frequency division multipleaccess (FDMA) network or code division multiple access (CDMA) network.The cellular network may include mobile devices, cell sites, basestations, repeaters, antennas, towers, and the like.

The methods, programs codes, and instructions described herein andelsewhere may be implemented on or through mobile devices. The mobiledevices may include navigation devices, cell phones, mobile phones,mobile personal digital assistants, laptops, palmtops, netbooks, pagers,electronic books readers, music players and the like. These devices mayinclude, apart from other components, a storage medium such as a flashmemory, buffer, RAM, ROM and one or more computing devices. Thecomputing devices associated with mobile devices may be enabled toexecute program codes, methods, and instructions stored thereon.Alternatively, the mobile devices may be configured to executeinstructions in collaboration with other devices. The mobile devices maycommunicate with base stations interfaced with servers and configured toexecute program codes. The mobile devices may communicate on a peer topeer network, mesh network, or other communications network. The programcode may be stored on the storage medium associated with the server andexecuted by a computing device embedded within the server. The basestation may include a computing device and a storage medium. The storagedevice may store program codes and instructions executed by thecomputing devices associated with the base station.

The computer software, program codes, and/or instructions may be storedand/or accessed on machine readable transitory and/or non-transitorymedia that may include: computer components, devices, and recordingmedia that retain digital data used for computing for some interval oftime; semiconductor storage known as random access memory (RAM); massstorage typically for more permanent storage, such as optical discs,forms of magnetic storage like hard disks, tapes, drums, cards and othertypes; processor registers, cache memory, volatile memory, non-volatilememory; optical storage such as CD, DVD; removable media such as flashmemory (e.g. USB sticks or keys), floppy disks, magnetic tape, papertape, punch cards, standalone RAM disks, Zip drives, removable massstorage, off-line, and the like; other computer memory such as dynamicmemory, static memory, read/write storage, mutable storage, read only,random access, sequential access, location addressable, fileaddressable, content addressable, network attached storage, storage areanetwork, bar codes, magnetic ink, and the like.

The methods and systems described herein may transform physical and/oror intangible items from one state to another. The methods and systemsdescribed herein may also transform data representing physical and/orintangible items from one state to another.

The elements described and depicted herein, including in flow charts andblock diagrams throughout the figures, imply logical boundaries betweenthe elements. However, according to software or hardware engineeringpractices, the depicted elements and the functions thereof may beimplemented on machines through computer executable transitory and/ornon-transitory media having a processor capable of executing programinstructions stored thereon as a monolithic software structure, asstandalone software modules, or as modules that employ externalroutines, code, services, and so forth, or any combination of these, andall such implementations may be within the scope of the presentdisclosure. Examples of such machines may include, but may not belimited to, personal digital assistants, laptops, personal computers,mobile phones, other handheld computing devices, medical equipment,wired or wireless communication devices, transducers, chips,calculators, satellites, tablet PCs, electronic books, gadgets,electronic devices, devices having artificial intelligence, computingdevices, networking equipment, servers, routers and the like.Furthermore, the elements depicted in the flow chart and block diagramsor any other logical component may be implemented on a machine capableof executing program instructions. Thus, while the foregoing drawingsand descriptions set forth functional aspects of the disclosed systems,no particular arrangement of software for implementing these functionalaspects should be inferred from these descriptions unless explicitlystated or otherwise clear from the context. Similarly, it will beappreciated that the various steps identified and described above may bevaried, and that the order of steps may be adapted to particularapplications of the techniques disclosed herein. All such variations andmodifications are intended to fall within the scope of this disclosure.As such, the depiction and/or description of an order for various stepsshould not be understood to require a particular order of execution forthose steps, unless required by a particular application, or explicitlystated or otherwise clear from the context.

The methods and/or processes described above, and steps thereof, may berealized in hardware, software or any combination of hardware andsoftware suitable for a particular application. The hardware may includea dedicated computing device or specific computing device or particularaspect or component of a specific computing device. The processes may berealized in one or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable device, along with internal and/or external memory. Theprocesses may also, or instead, be embodied in an application specificintegrated circuit, a programmable gate array, programmable array logic,or any other device or combination of devices that may be configured toprocess electronic signals. It will further be appreciated that one ormore of the processes may be realized as a computer executable codecapable of being executed on a machine readable medium.

The computer executable code may be created using a structuredprogramming language such as C, an object oriented programming languagesuch as C++, or any other high-level or low-level programming language(including assembly languages, hardware description languages, anddatabase programming languages and technologies) that may be stored,compiled or interpreted to run on one of the above devices, as well asheterogeneous combinations of processors, processor architectures, orcombinations of different hardware and software, or any other machinecapable of executing program instructions.

Thus, in one aspect, each method described above and combinationsthereof may be embodied in computer executable code that, when executingon one or more computing devices, performs the steps thereof. In anotheraspect, the methods may be embodied in systems that perform the stepsthereof, and may be distributed across devices in a number of ways, orall of the functionality may be integrated into a dedicated, standalonedevice or other hardware. In another aspect, the means for performingthe steps associated with the processes described above may include anyof the hardware and/or software described above. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

While the disclosure has been disclosed in connection with the preferredembodiments shown and described in detail, various modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present disclosure isnot to be limited by the foregoing examples, but is to be understood inthe broadest sense allowable by law.

What is claimed is:
 1. A portable electrochemical gas sensing apparatus,comprising: a housing comprising an exterior surface that defines aninterior space, wherein at least one depression is formed in theexterior surface; an electrochemical gas sensor at least partiallydisposed within the at least one depression of the housing; and aprocessing unit disposed in the interior space of the housing and inelectrical communication with the electrochemical gas sensor, whereinthe electrochemical gas sensor comprises an electrode stack, wherein theelectrode stack comprises at least one gas permeable membrane, at leastone electrolyte absorption pad, at least one measuring electrode, and atleast one counter electrode.
 2. The apparatus of claim 1, furthercomprising, at least one reference electrode.
 3. A portableelectrochemical gas sensing apparatus, comprising: a housing comprisingan exterior surface that defines an interior space, wherein at least onedepression is formed in the exterior surface; an electrochemical gassensor at least partially disposed within the at least one depression ofthe housing; and a processing unit disposed in the interior space of thehousing and in electrical communication with the electrochemical gassensor, wherein the at least one depression comprises a first reservoir,a second reservoir, and a centrally-disposed raised platform formedwithin the at least one depression of the exterior surface, and thecentrally-disposed raised platform is shaped to support, at least inpart, an electrode stack.
 4. The apparatus of claim 3, wherein theelectrode stack rests on the centrally-disposed raised platform andcovers the second reservoir.
 5. The apparatus of claim 3, wherein thesecond reservoir is adapted to hold an electrolyte solution that is influid communication with the electrode stack.
 6. The apparatus of claim1, wherein the electrode stack is in electrical communication with analarm modality, wherein the alarm modality is disposed in the interiorspace of the housing.
 7. The apparatus of claim 6, wherein the alarmmodality is wirelessly connected to the processing unit.
 8. Theapparatus of claim 3, further comprising a cap sized to fit over the atleast one depression.
 9. The apparatus of claim 8, wherein the capcomprises a capillary hole providing access for gas entry into theelectrode stack.
 10. A portable combustible lower explosive limit (LEL)gas sensing apparatus, comprising: a housing comprising an exteriorsurface and that defines an interior space, wherein at least onedepression is formed in the exterior surface; a combustible gas sensorat least partially disposed within the at least one depression of thehousing; and a processing unit disposed in the interior space of thehousing and in electrical communication with the combustible gas sensor,wherein the at least one depression holds at least one catalytic sensingbead in a chamber.
 11. The apparatus of claim 10, wherein the at leastone catalytic sensing bead is in electrical communication withcomponents of the apparatus disposed in the interior space.
 12. Theapparatus of claim 10, wherein the at least one depression comprises twochambers with a chamber separator integrally formed in the at least onedepression, wherein each chamber is adapted to hold at least onecatalytic sensing bead.
 13. The apparatus of claim 10, furthercomprising a sensor flame arrestor that covers the at least onedepression.
 14. The apparatus of claim 10, wherein the combustible gassensor comprises: a gas sensing element including: an electric heatingelement, a first layer coated on the electric heating element andcomprising a precious metal catalyst supported on a porous oxide, theprecious metal catalyst catalyzing combustion of a combustible gas to bedetected by the gas sensing element, and a second layer overlaying thefirst layer, and comprising a catalytic compound capable of trappinggases that poison the precious metal catalyst, said catalytic compoundbeing supported on a porous oxide; a compensating element comprising anelectric heating element, said compensating element not including acatalyst capable of catalyzing combustion of a combustible gas to bedetected by the gas sensing element; and a processing unit to which thegas sensing element and compensating element are connected, theprocessing unit being constructed and arranged to detect changes inresistance of the gas sensing element and compensating element, and toprovide a reading of said changes.
 15. The apparatus of claim 14,wherein at least one of the precious metal catalyst and the catalyticcompound comprises an oxide-supported metal oxide supported on at leastone of a porous oxide support, a solid acid, a solid base, ametal-loaded zeolite or a metal-loaded clay.